How about a permanented (or maybe, immovable because it is activated by something too large to move, like an obelisk) Mordenkainen's Magnificent Mansion (PHB p256, Mage's Magnificent Mansion in SRD)? It's a 7th level spell, it is nearly perfectly safe (it can be entered only through ONE portal, which only opens at caster's will). It's a perfect lodge, and if you bind it to the place, it becomes a great safehouse...
Which can be destroyed by Mordenkainen's Disjunction (PHB p255, Mage's Disjunction in SRD), a 9th level spell which automatically dispells all the magic in the area, makes every magic item to make a Will save or be turned into a mundane item and even has a chance of destroying artifacts. The key here is to make sure that all the PC and their gear are at the other side of the Mansion and the demons do not know about that, which will guarantee that nobody would loose any important magic items.
So, in short: Place a statue/obelisk/something else too large to move (or known to lose its power if moved) in the city, let the party activate it to grant them lodging, access to a treasury and the other things you think they need, and let them enjoy that large house for a while. Perhaps it is even activated and deactivated by a treasure the party removed from the dungeon, providing them with a key to the mansion. Then, when you think the time is right, dispel it with Mordekainen's Disjunction (which would be even more surprising if the house had successfully resisted some really hard hits) and let the players suddenly face that high-level encounter 8)
The key to encounter design is that an encounter (whether it involve combat, riddles, or some other task) has to be interesting to spend time on it. The reason the players will probably enjoy the task of obtaining the wolf's pelt is because it's both fairly broad (one possible option is to find a nearby village and just buy one and that would take seconds of ingame time, because it's not fairly interesting) and because it's inherently interesting. After all; the wolf's pelt is attached to the wolf, and the wolf has sharp teeth and a desire to not be seperated from its pelt, which turns the situation into a conflict.
(Conflict being the key word, because conflict is what makes the game interesting)
But the task of cutting down trees isn't a conflict. And as such, while it takes a lot of time, it isn't inherently interesting. This in turn means that players won't spend much time on it, and shouldn't spend much time on it, because it's a boring part of the campaign.
So the goal of the encounter design shouldn't neccesarily be that the task isn't trivial, but rather than performing the task should be interesting to the players. Introducing some form of conflict or complication will make players want to invest more time in figuring out and solving the problem.
I'm going to assume the crazy old hermit lives in the wilderniss and outside of civilization. Below is a list of possibilities to make the trivial and boring task of "cut wood for winter" more interesting.
- The hermit lives on top of a hard to traverse hill with a small bridge leading to his home. Cutting down the trees isn't an issue. Getting them to him, will be.
- The nearest wood is hours away. There are no tools available to transport the wood back all that distance, and there's no time to do it the hard way.
- Most of the trees in the local area struck by some kind of disease and would not burn. (or be dangerous when burned). Either the players need to fix the disease, or they need to figure out how to find healthy trees.
- The wood is protected by Elves/Druids/Treants/Whatever and they aren't really interested in having them cut down by random people. They'll need convincing in some way.
- The hermit doesn't actually have any woodcutting tools. Or a storage place. Or a fireplace. Why the hell does he want us to cut wood anyway? What is he up to?
You can try the same kinds of tricks for other tasks. The key is to make them interesting, by introducing complications that rule out the simple solutions. Think over the steps needed to complete a task ("find tree", "cut down tree", "drag tree back") and then add reasons why it isn't as simple as saying these things in a row to fix the problem ("there are no trees to be seen", "the tree has DR 20/adamantine", "it's heavy as hell") and then make the players figure out how to get around the problem. Try to introduce issues that make sense story-wise and the players will probably enjoy fixing them.
It doesn't have to neccesarily take effort on behalf of the players or their characters, but the key is to make the solution non-straightforward. This forces them to come up with a plan, which will increase game time needed.
The more game time you need, the more or bigger complications you will need to introduce in order to stretch things long enough. You can even start combining complications, for bigger issues. At some point, you can introduce so many complications that even a simple task like "cut some wood" can turn into an adventure in itself, although you must of course be careful that your players will not at some point tell the hermit to stick it where the sun don't shine and leave.
Best Answer
Teamwork, resources, environment, and planning.
Defenders have a tremendous advantage. They don't have to carry stuff in. They don't have to scout. And they have reserves.
Defenders with an established structure have all sorts of capital:
Human Capital
Human capital is the first trick. An adventuring party is fundamentally limited in the number of people they have. These people have relatively limited resources attached to them. There are expenditures, but the nature of adventuring life is that most resources are dropped into incredibly inefficient gear because of the number of hands available to hold it.
By breaking away from the adventuring life and investing in people, you fundamentally get more actions per round. Now, while at much higher levels a capable tier-1 caster laughs at a horde of underlings, there are many things to be feared from a structure that communicates.
At the end of the day, hiring guards based on their ability to Use Magic Device and issuing them all wands of Magic missle is a huge advantage. You don't need to worry about accuracy, and 4 people with a wand of magic missle are far far cheaper than a high level wand.
More to the point, by having purely-defensive people in place and allocating them their own resources for defense means that you don't even need to worry about defensive measures for your offensive folks.
What's even better is that these resources sit around. From the relative cost scales of higher-level gear... if you need to use these resources, you'll probably capture more than their value from the idiots you're using them against.
As a means of insurance, having spells to take care most of the more common problems (adventurers being top of the list) you can amortize the risk and therefore the cost of adventurers over weeks and months, instead of having to pay for the acute cost of repairs.
From a technical point of view, you want to invest in level 1 stuff for most of your mooks. One shot potions, poisons, and wands are absolutely fantastic for this sort of thing. They sit around until they're needed, and there's no worry of "should I save it for later."
Details on loadout:
Infrastructure
Infrastructure is a kind of investment that is nominally impossible or not particularly useful for adventurers. There are different roles for structure, but protection and subdual is the critical aspect here.
The critical thing here is to allow them an "out" so that they aren't forced onto deadly ground. Instead, the architecture should make it harder to go to important places and easier to go to exterior places.
Of course, these exterior places, not being frequented by the public, can have various man-traps (sally ports and whatnot) to thereby contain adventurers in a safe (to the infrastructure) location for handling. But giving them an escape route into this area is critical so that they don't stick around and damage important bits.
Therefore, infrastructure is something that can take as muh money as you want to put into it, and will repay the hotel handsomely.
Features of infrastructure are a function of the role that you want the infrastructure to play
Roles of infrastructure
Temporal capital
There are two types of temporal capital. Planning and the action economy. The greatest luxury that your environment will have is the ability to have a very short OODA loop. With a plan, the reactions of the opposition will get inside the adventurer's OODA loop leaving them with the feeling that they just need to di di mau because things are simply moving too quickly and the opponents are too well organized.
By having quick reaction forces in place with plans and alert signals, the hotel will completely violate the adventurers OODA loop and social construction of "dungeon." (as the idea of dungeon does not have mutually reinforcing and escalating waves to force people along a desired path. Because fairness.)
Temporal investments