The smaller dogs generally live longer, it turns out--but I'm more a big dog guy (have mostly had retrievers). My last, a Golden, was just an amazing friend, never mind the species. Loved all the animals I raised and lived with, but he was special.
Makes you realize why, much as I love to be alive and want to "see how it all turns out", in this fundamental way it would be a drag to be uniquely long-lived, to live for centuries, if everyone else, everyone you ever cared about, had "normal" lifespans. You'd watch them all inevitably falter, fade, then pass on. Eventually you'd have to harden yourself, not get emotionally involved with other people; ultimately you would walk through the years on the edge of life, seeing and existing, but not really "living" anymore.
As Henry Rollins put it:
"Life is cold and lonely, cruel and hard--AND TOO DAMN SHORT!"
To live it, love it and really get the most out of it, you have to risk and accept the pain and loss.