Are they indoor or outdoor cats? Why or why not?
We try to keep collars on everyone, especially M.K. (since she's indoor/outdoor) which usually means we're rotating them from cats that never go out to her. I'm a firm believer in break away collars, so I'm quite happy to just keep buying them as she looses them (plus we just get the hyper-reflective collars from the dollar store)
Right now Tasha (the one conveniently outside right now) is the only cat with a collar on. Oscar is too little (well maybe not any more) and M.K. & Peaches took theirs off awhile ago.