The book "Horizon: Stronghold of Hope"... or some title like that, titled at least on the Horizon Chantry... has some backgrounds and things specific to archmages.

I don't know what the Age background gives, but mages can be as long-lived as a vampire. At least in the modern era, they get 1 permanent Paradox per every 50 years old they are after 100 (so 1 at 150, 2 at 200, and so on.) I don't know if that would be in effect in the middle ages, but I imagine it would to a lesser degree. That'd be the downside of being very old but living on earth.

Also, looking young is easy (Life 3, I reckon), but I think it's a convoluted rote to actually refresh your mind and body metaphysically so that you do not go insane/senile. I think I heard "Masters of the Art" has that rote described.

Note: as the Mage books contradict one another in some of the specifics, all of the above might be contradicted or done slightly differently in another book.