I generally assume creatures with Might are immortal (aging-wise), unless specifically stated otherwise. Nephilim specifically are described as "age-less, but can eventually die although they may live for thousands of years" (RoP:tD, non-revised version if it makes a difference). That says, their stats do change with age, so it still needs to be tracked. Blood of the Nephilim (which is a pre-requisite for Strong Angelic Heritage) gives some restrictions on learning once you get your first decrepitude point.
One potential can of worms I'd be wary about is to make sure you and your troupe/gm have the same understanding of what being a Divine Being means in terms of the requirement(s) for morality in your actions.