It depends on who you ask, some say 6 months, other say a year. Personally I think they can start having playtime by the time they are 6 months (as well as higher ledges, and a chin safe wheel to run on), before 6 months no more then 5-10 minutes a couple times a week. Just keep an eye on them for signs of over heating or over doing it, things like ears getting red, heavy breathing, flopping over, stuff like that, as well as monitor their weight. It's also best to start doing playtime slowly, like only 15-20 minutes at first, to see what they are like when out, then work up to longer. Some chins are go go go, nonstop when they are out and will play until they literally drop, and need to be told when to stop and put back in their cage. Others are laid back and will bounce/run around for a bit but then sit and chew on some stuff for abit, then go back to playing, and they can have longer playtime without worry of over doing it.
