Luna is one year old. Since she was a kitten, when she plays hard, chasing her string toy all over and jumping after it, she starts panting. I mentioned it to the vet on 2 occasions and they inspected her nose and listened to her lungs and said there was nothing abnormal. She also used to snore but I haven't noticed that anymore. She never stops playing, I always put the toy away when she starts panting, if I didn't I think she would play until she drops! So, her energy level is good. I have never seen a cat pant before and it seems like she doesn't get much play time.