I've got 4 GALS that are about 1 1/2 yrs old. I tend to feed them on whatever peelings, veg, salad we have going so they get a good variety of food. I also use coco blocks and keep it moist by spraying it regularly. I keep them in a large RUB that isn't heated (although the house is always warm as the wife has the heating on constantly) and they're really active (for snails).
Never thought of giving them a bath but they do crawl through their water bowl so they bath themselves. Ours have only sealed up once before and we thought they were dead
but they've been fine since.