too much fun?

Ok, this may sound dumb, but can a cat play too much? Holden loves Da Bird. In fact, he plays until he is panting like mad! Is it safe to continue to play when he pants or should I stop and let him calm down? He is a baby still (7 months) and I don't want to over exert him or cause him harm. Am I being overly protective or is it reasonable? Just curious..my first cat..I don't know much!

I asked this question when Daphne was small. She started out panting after 5 minutes or so. As she got older, the time until she started panting got longer. People here suggested stopping the play when she began panting and waiting for her breathing to return to normal. Now she is almost a year and never pants when playing. She wears me out

(hope this makes sense - am sleepy )