Do some dogs "pant" harder & longer than others? My 2 yr YLF seems to pant long & hard after a workout of maybe 15 minutes, doing marks, blinds & simply running around for some exercise. It is probably my imagination, but concerns me some. I will take her to the Vet for a check...otherwise acts very healthy & happy. Her heavy panting may last fifteen minutes....has been on heartworm from day one.