In an interview with SFX, Russell T Davies addressed the fandom-splitting line in the recent Sarah Jane Adventures episode, Death of the Doctor
, which supposedly changed the regeneration limit to... 507.
"507 Ė I could not resist! I was hooting. Itíll never stick, though. That 13 lives is stuck in peopleís heads. It is, isnít it funny? Yet they only said 13 once or twice."
Read the rest of the interview here
, where Russell talks about writing for Matt Smith's Doctor amongst other stuff.