Brewed a 10% abv Imperial Stout in June and have been letting it mellow in the fermenter now for 4 months. With the higher abv and the aging, wondering if I should add yeast when adding corn sugar when bottling. Looking for some advice with this situation. Cheers!
Assuming that 10% ABV is well within the normal alcohol tolerance of your original yeast strain, you probably don't need to add yeast at bottling. But if you want to add some yeast for insurance, go ahead. Just make sure the strain you add is not more attenuative than your original strain. CBC-1 would be good, because it doesn't eat maltotriose and has a very high alcohol tolerance.
Yes add yeast. You don't need to add a lot. Just about 1/4 as much as normal, maybe even a little less, is sufficient to achieve carbonation at bottling. I've done this many many times.