I dunno...it seems as if literally nobody questions his longevity nor the fact he looks remarkably fit and healthy for a man his age. It seems as if there's some precedent for men living over 150, and that sorcery seems to be an easily accepted explanation.
I'm just saying it's not entirely improbable that some person or persons of mannish descent has prolonged his or her life using sorcery before. Certainly not to the extent of a Telvanni wizard but long enough to be notable.
Not impossible but improbable. Don't you think we would have heard of mannish sorcerors that powerful. Again, people, especially medieval people believe the silliest things. Egyptians actually thought that there Pharoahs were gods, many peoples actually believed in sea monsters, and for thousands of years, no one really questioned any of the religions. And again, we don't know the initial reaction. Maybe they were shocked at first, and now assume he IS the precedent, and he is the first mannish sorcerer to be able to do it.
All of his inner circle at the castle obviously know, but if they've told anyone, it's not apparent in the rumor mill. You may well be right that he's known as a vampire, but everyone seems to accept that he's a sorcerer. That's what leads me to believe it's not unheard of for powerful wizards to extend their age, even without using necromancy.
You really think that his inner circle never told anyone? What about the ones that are not there anymore. What about the families. I always kind of assumed most people knew, but didn't care to bring up, because they were happy. And nothing that isn't directly related to you is in the rumor mill in Oblivion. Everything is related to you or a quest. Not reliable. Plus, I'm sure be this point it's old news. And the Emporer and Ocato must have known as well.
Certain potions, enchantments, gems or spells from the Restoration school might possibly aid a person in slowing down the effects of age. A certain variety of resist disease or fortify health/fatigue, perhaps.
Yes, but men deteriorate much quicker without help from disease. We still don't know how long a mer can live without magic or disease. Barenziah is 450 and healthy, and she is just an aristocrat. We know men will die from just old age and a deteriorated body around 100. Even Dunmer can last at least 350 years more. All they have to is prolonge 450 years to 1000 opposed to 100.