Its the same with humans though. There are many things you're supposed to be tested for when you reach 40-50 because they are common with those age people. Young people are less likely to get cancer and other diseases...
With me, Chloe got cancer around 5-6, Izzy got a tumor in his testicles at 5 (though that isn't what killed him-an incompetent vet killed him by squeezing his abscess), Raven mysteriously died at 4, Ginger died mysteriously around 4, Bonnie died mysteriously when she was about 5-6, Sugar died of old age around 7. I think Lily died of old age at around 5, but she was a giant.