i have 2 cats (13 and 15 years old), and one of them has always been an indoor cat, and the other one has been indoor for the last 6 years (not letting her out in nyc!). and it was pretty much just before then that she became a total sleepytime cat. she's always been a lapcat/lounger, but its definitely turned into a fulltime occupation. some cats though are definitely still frisky into their older years, just like some people i guess, all depends on their temperment and personality. one of mine is a lazy bum, and the other is diabetic, so he's actually in shape mainly because of diet than what little exercise they get in my apt.