When I read that line in the manga when Ed is about to perform human transmutation on himself after getting pierced through the chest I wondered about that--"this will probably shorten my lifespan..." after which he mysteriously grew taller and older-looking (Ed looks more in his 20's now in a lot of scenes and he's now taller than Winry--although Arakawa then turns around and draws him like a little kid--bugs me how she goes back and forth all the time). I for one like to think that since he's Hohenheim's son and Hohenheim is NOT a normal human, that Ed and Al will have longer lifespans...something I've used as a major part of the PostHagaren Alt!Verse I've created, inspired by that OVA stating that in the year 2005 Ed would be a hundred years old--and he hasn't got a single grey hair!