Tennant has been The Doctor in pretty much 50 episodes by the time he regenerates (13 episodes x 3 + 3 Xmas Specials + 4 2009 Specials + "Born Again", "Attack of the Graske", "Music of the Spheres", and "Time Crash"). That's a large volume for a short period of time, thus it seems like he's been around longer than he has, actually. I agree it's time for him to go. Go out on top. Don't wait until he's worn out the welcome. He leaves now, and we remember the enthusiastic Doctor Who fan who actually got to live the dream. I will always prefer Tom Baker in
City of Death over Tom Baker in his final season...