I have no idea why but all of our pets over the years have lived a long and healthy life. Two previous, medium breed dogs made it to 15. Two previous cats, to 18 and 19. Never an illness nor vet bill other then the regular shots. These two seem to be no exception. Jake is heading towards 13 and Christopher turned 20 in January. For the past 3 Summers we have told him, as he lounged out on the porch, "Enjoy it while you can cat, I'm sure it's your last". He is in great shape, so it looks like he's holding on for at least one more Summer of chasing dogs and cats off the property and sleeping in the sunshine.