I don't ever let my cats outside. I have some "porch kitties" (i.e., strays that I feed) and I recently had to put one of them down. It seems that he got into something that was poisoneous (perhaps anti-freeze) and he was suffering terribly before I took him in. If you have the option I would definitely try to keep them as indoor only cats. Speaking from experience I can tell you that it is difficult to put a friend down