I am wondering what truly happens if I leave my IPA in the fermenter....even after the GF has set at a stable, bottling level. Will the yeast actually do something to the batch that is either good or bad?
I am asking because I cant bottle for 3 weeks (counting from the brewing day) due to being to busy. And I guess this batch will be surely ready in 2 weeks time.
It's actually beneficial to leave it on the yeast cake for a week or two. The yeast will reabsorb some of the flavor components that are not favorable in the beer.
From John Palmer's How to Brew:
Leaving an ale beer in the primary fermentor for a total of 2-3 weeks (instead of just the one week most canned kits recommend), will provide time for the conditioning reactions and improve the beer. This extra time will also let more sediment settle out before bottling, resulting in a clearer beer and easier pouring. And, three weeks in the primary fermentor is usually not enough time for off-flavors to occur.