That "stat" surprised me as well -- small dogs @ 10 years and large ones at 17? Uh, no.

Great danes and Irish wolfhounds (and other big breeds as well, AFAIK) only average something sad like 7 years, whereas those little yappy toy poodles average twice that.

Along those lines, smaller versions of the same species live longer than large versions. Dogs as you point out, but also cats, and humans. Look at mortality rates for 7 footers as a good example.