[beowulfey]

That’s also an interesting anticorrelation with how we normally relate metabolism and body size; smalller organisms tend to have faster metabolisms and live shorter lives versus much larger organisms.

Maybe the key is being smaller but also having slower (or rather, “calmer”) metabolic rates.

[DFHippie]

I believe what you want to be is a small member of a large species. Large dogs live much shorter lives than small dogs. Women tend to live longer than men (height or mass probably isn't the only factor here, but this fits the general pattern so one imagines it helps). Giants -- people well over six feet -- tend to live shorter lives than people of ordinary stature. My grandmother was about five feet with a straight spine. With a curved spine in her early hundreds she was probably less than 4'6", but she was still there. She had about two giant lifetimes. If you stacked her on top of herself you would have one giant (until her ever more flexible spine folded in two).