Out-of-universe, the Eighth Doctor was played by Paul McGann in the TV movie (his only televised appearance), the webcast version of "Shada" (his only animated appearance), and a series of Big Finish audio plays.
The Eighth Doctor also starred in the last Virgin New Adventures novel, a series of BBC Eighth Doctor Adventures novels, and a variety of other print forms (Short Trips collections, Telos novellas, DWM comic strips, etc.).
Until 2003, he was the "current" Doctor; the novels, audios, etc. Were chronicling his life the same way the TV series is currently doing for the Eleventh Doctor. After that, it was decided to create either a series of films or a new animated series, with a new Doctor either way; neither of those panned out, but instead we got the revived TV series with a new Doctor, which started in 2005. Since then, any Eighth Doctor stories have been the same as other "past Doctor" stories, set in gaps in his past. Paul McGann has continued to appear in such stories for Big Finish (just like Tom Baker, Peter Davison, Colin Baker, and Sylvester McCoy).
McGann appeared on-screen again in "The Night of the Doctor" (a prequel to the 50th anniversary special) in 2013. Via archive footage, he also appeared in "The Name of the Doctor" (the Series 7 finalé) & in "The Day of the Doctor" ( the 50th anniversary special).
Eighth Doctor's Life Edit
Probably at least 1023 years, but maybe not.
And that's the best answer you'll ever get.
The BBC 8th Doctor Adventures novels document at least 119 years of his life, but they also throw into question the Doctor's ability to count his age or keep track of time (especially since he became an amnesiac multiple times), and it's never stated how long the last batch of novels took, how long it was from the last novel until the Last Great Time War, or how long the War took. The Big Finish New Eighth Doctor Adventures audios document at least 903 years of his life. (The comics, and some of the earlier Big Finish audios, generally fit into a 3-year gap already provided by the novels.)
In fact, nobody knows exactly how long any of the Doctor's incarnations lived, because they all have gaps at different points in their career where it's impossible to guess how much time passed. (This is why the Virgin Missing Adventures and BBC Past Doctor Adventures books could be written.)
While the Doctor does sometimes give people his age, the ages are contradictory. Plus, he's been caught lying about it, and has said that he can't remember or keep track.
As show-runner Steven Moffat said in an interview:
- The thing I keep banging on about is that he doesn't know what age he is. He's lying. How could he know, unless he's marking it on a wall? He could be 8,000 years old, he could be a million. He has no clue. The calendar will give him no clues.