They live slightly longer, but I'm pretty sure they do age. I don't remember the exact words Heart-Fang says, but I found the journal note about it.
I told Heart-Fang that, as there could only be one survivor in this deadly game, I could not work with him. He responded that he alone would survive this Hunt, and that it was his birthright to do so. Apparenty, Heart-Fang has the Ring of Hircine, and has used its magic to prolong his life and rule the Skaal for generations. Now, he claims I will have to face him in his "true form."
- Journal Note, Bloodmoon.
Now that isn't conclusive, as perhaps the ring also prolongs life as another effect, but it seems likely that being a werewolf extends a person's life(Until some champion decides to kill them of course).