Really? I think there is like only one transition from one game to the other that could bring you character back to an acceptable age to play. The first four games were all within the life span of Emperor Uriel Septim VII. With Oblivion he could be the same person from Morrowind if you didn't make him the Nerevarine.
Yes, he could be the same person, but then I would have to invent a mechanic to explain how he goes from very skilled to knowing almost nothing about anything. From very rich to destitute.
The reincarnation thing allows me to play the same character, who for instance knows he likes destruction, but isnt good at it at first.
And he is an acceptable age to play as his reincarnations are linear to him, but not compared to the actual timeline.
He hops around a bit.
its like a big ball of wibbly-wobbly.. timey-wimey.. stuff..
And its fun having him be annoyed at having to train his skills up to save the world.. again.