I've always like the idea of the dragonborn being someone who can never age, as long as he/she doesn't get killed they could live indefinately without worrying about growing old and frail. Is there any basis lorewise for this being the case. Would the dragonborn still be kicking centuries down the line as long as they could keep themselves from getting killed.

Not really. Soul of a dragon, but body of a mortal. And having a mortal body means that you are, well... Mortal. If you are a Mer, you might live for a few centuries. If you are a powerful mage, maybe a few thousands. But you're not immortal, unless you're a vampire.

No basis for this, as far as we can tell.

Basically, a Dragonborn is a mortal with a Dragon's soul. That means they can die of old age. Remember, all Emperors in the Septum line were Dragonborn; most died of old age, and Uriel Septum was visibly aged when we meet him.

If you want, you can RP as the Nerevarine. The Nerevarine has Corpus disease, which makes them immortal (and immune to diseases.) And there's no lore conflict with the Nerevarine being a Dragonborn (since they never met any dragons... as far as we know.)

This is the question hey. The Dragonborn is the character, but how is that going to resolve in the next game in the series. I'm thinking the Dragonborn is going to withdraw the THUM from Tamriel and leave with the Dragons for other realms . Maybe.

Aren't Werewolves technically Immortal like vampires? If not, how long do Khajiits live? Either way, I live a pretty long time.

nope werewolves are not immortal they may live a few more years then the mortals but they end up dying with age too khajiits probably live until 100. If they dont get an Overdose much sooner