Would Nathan's immortality have kept him from aging?

The title is self explanatory, would he had stayed eternally young if he hadn't sold his powers, or would he had continued aging and just been unable to die? I know it's never actually explained in the show(at least, not as far as I remember) but how do you imagine it working? Through some other more convuluted way where he'd return to his prime everytime he dies, or would he just shrivel up like a roach at a 100 years and still been conscious?