Totally depends on the personal canon. My own sifted over time and I’d say closer to 8-10 years myself now. But I also feel like fluffies as a concept is old enough now that they could have evolved in (at least my own) canon. So the original Hasbio Fluffy would have lasted 5 years due to planned obsolescence, but breeding in the wild selected for some toughness and longevity as well as hobby breeding.
For this comic I really just wanted to do a gut punch to the feelings so 5 years was about right. Old enough for the boy to take care and bond with a pet and still young enough that it could still be a best friend when it died.
For a story about an old fluffy: The Oldest Fluffy (author_jberg360)