This wiki contains all you need to know about trees, shrubs, bushes, and rocks, also known as 'obstacles'.
There is one small benefit to keeping them, an attacker cannot spawn troops on top of an obstacle. However, this benefit is trivial at best.
There are much greater benefits for removing them, gems and experience! You can get a small amount of gems and experience for removing and continuing to remove these obstacles. There is even the 'Nice and Tidy' achievement which will give you additional benefits after clearing 5, 50, and 5000 obstacles.
And you never see benefits from the workers gathering stuff from the vegetation. Theoretically they are feeding themselves. But gems are much more important than fed workers!
I'm in a similar situation (albeit at TH7). I've got half my walls yet to upgrade, which is going to cost many millions in gold. However, I just finished my last lab upgrade and don't have that much left to spend massive amounts of elixir on.
You've touched on higher cost raids in your question. It is true that BAM/BARCH is a solid strategy, but it is very low cost in terms of elixir.
Right now you might want to focus on dark elixir and gold, so you may want to completely trash bigger, better defended bases for maximum loot. Dragons take a crazy long time to train, but you might consider Giant/Healer or perhaps Balloonian raids to give you a bit more destructive potential and use up some of that elixir.
Having a whole bunch of elixir in your storages deep inside your base is a good way to get raided and completely trashed. This is going to cost you gold and dark elixir, which is a bad thing.
Right now I've got my elixir storages outside of my walls, and I like that pretty well. I've trapped them heavily, to get people to commit a lot of their troops to taking them down. This tends to end with me earning trophies from them at a cost of elixir. This has two benefits:
- Gaining trophies, which will give you bigger fish to fry when raiding and let you occasionally take resources from bases without getting a star
- Give you "sucker bases" to revenge when you're online. Revenge is a powerful tool for finding bases where you can take your time, plan out a strategy, and take their stuff.
I wouldn't suggest preemptively upgrading your town hall unless you're sure you're ready for it. Some of my clanmates have moved up early and found that the resource penalty causes them major issues. This lengthens the time it takes to get enough resources together to make your upgrades.
Best Answer
For the 2014 Holiday season: no, there will be no more presents spawning.
If you tap on the settings icon (bottom right), and then tap on the News tab, you should see a news entry titled "Happy New Year, Cheif!" The text of the entry states that the Holiday events are over and that the Christmas trees have stopped spawning gifts. In addition, I haven't seen any new presents spawn for several days, since that news entry was pushed out to players.
As soon as a builder of mine frees up, I'll chop the 5 trees currently residing in my village.