Panting episodes

my (30, Canada) neutered orange boy (11 months) has been having panting episodes. it started a few weeks (June, I think) ago at the end of heavy play, and through research online I thought the sub-10 second panting bouts were fine. then I went on a trip for about a week- looked after by my roommates. I came back after a week and he caught a mouse about 10-20 mins after play time and had a much longer panting (40 plus seconds heavy panting on and off for a bit- first time I’ve seen it) episode so I went to the emergency vet. they deemed he was just excited from the mouse and over stimulated himself. This included a chest ultra sound with no signs of fluid or heart disease.

about a week later on a 30 degree (inside plus high humid day- felt like 38, I was sitting still, sweat in places I didnt know I could ) he had a full day of multiple 20/30 seconds panting episodes (all with some sort of play/movement but even if minor- none at relaxed state) so I called the emergency vet with videos from all day - the on call vet stood by the firsts diagnosis, and probably just good at regulating temperature. I bought him a cooling mat, and he seemed to appreciate cool water

since then I might have seen one/two short episodes a day but I’ve also been at work so things could be missed.

tldr;all have been with some sort of active prompting but happen fairly soon into activity. including quick into his own zoomies.

he hasn’t panted during his fave game (run for kibble) but in nervous bringing out the wand toys that he will start the panting again - could he have gotten out of shape so quickly while I was gone?

today my friend came over and played fairly hard and short with him and he panted for a bit. but again, short bouts in a short time frame with quick recovery but brought on quickly. is was only 26 degrees inside, but my friend mentioned how warm she found it.

he has an appo for his first birthday in two weeks (with blood tests) but I can’t keep taking him to the emergency vet and spending $250 every few days before then. I really can’t afford that. any thought are appreciated.