The nice thing with these older adult females is they can still have a useful life in your rat colony even if not as active, producing breeders. My older females aka granny rats keep the breeder females company when they are resting between litters, they sometimes go in the female feeder/grower bins to settle down an overly active group of feeders and they help me raise up my next generation of female feeders by helping me socialize the new girls. Rats like to stay busy, like to be in their social groups, etc. so I find that these roles for my older females help them stay active and healthy.