My observations in the Auction House do indeed show there is server-side caching going on with requests. My completely uneducated guesstimate is it will refresh your cache approximately every 60 seconds. However, there is a way around that:
Let's say you're looking for a cheap item with a buyout of less than 5000. Do your first search on 5000. Then re-search with 5001. Then 5002, and so on. The reason why I say this works is researching the same amounts over and over again always return the same response through the first 60 seconds or so. If I change my max buyout amount, I WILL find items listed that I didn't see before that match the previous criteria (i.e. change my max buyout from 5000 to 5001, and an item with a max buyout of 1499 will show up.)
Hopefully this helps.
EDIT: I realized on re-reading I need to clarify something. What caches with the AH is the specific items listed, not the time left in auction or the ability to buy them. When you refresh the identical query over and over again, if the item listed sold it will change to "Sold". The time left in the auction will appear to be the same. However, the query will not search for new items that meet your criteria, which is what the question is referring to.
Pound of Flesh Increases chance of finding a health globe by 25%, and you gain 100% additional life from health globes. This you already know, but to answer your question, it has the following effect:
The chance to drop increases by 25% of the original drop rate. As an example, a Hulking Phasebeast has a 60% drop rate, with a globe size of 20. With PoF, it will increase the drop rate by 15% (which is 25% of 60%), giving you a drop chance of 75% with a globe size of 20. The globe sizes aren't changed.
The 100% additional life form health globes effectly doubles any healing you receive from the globe when you or another player collects it. Item heal bonuses are calculated separately, so things like Life on Hit, or Life on Death are calculated and applied when those events happen. Picking up a globe is its own event.
All monsters, normal, rare, champion and unique will have their chances increased. For unique monsters which have a set number of drops (like Diablo,), then the only benefit you get is when you or another player collects those globes.
This passive skill still works if you are not the one dealing the killing blow. If you are close to a monster which is being killed - even by another player, the drop chance will still be increased, just like you will get experience from the kill, and just like you will get the kill registered in your massacre bonus (if any).
This effect does not stack if you have other barbarians in the game, just like Monk mantras of the same kind (e.g. Mantra of Evasion) do not stack.
Source: Diablo 3 Brady Games Guide, plus personal experience.
Best Answer
The legendary gem is consumed.
Legendary gems will continue to drop in Grifts as long as you don't have a copy of that gem on your active character, their companion, or in your stash.
Note that the list above is exhaustive. If a gem is on another of your characters or on the ground, it can drop in a GRift.