I imagine that if Eleven lived for roughly 900 years in his incarnation, then 1000 years is probably the upper limit for each regeneration, barring accidents, illness and exposure to elements that can deteriorate the body. If Eleven's testimony is meant to be taken as accurate, then the upper age limit for a Time Lord is probably somewhere between 10,000 and 13,000 years. The Doctor started saying he was only 900 when Colin Baker was in the role. Before that, I remember the Fourth doctor saying he was 750 during "The Pyramids of Mars". What we do know is that there could be vast swaths of time - centuries even, that are unaccounted for in many of the Doctor's lives.
Three could have spent a few centuries traveling after his pardon from the Time Lords between Jo Grant's departure and Sarah Jane's arrival. Heck, he flew off alone to Metebelis 3 while Jo was still his companion. He could have been traveling for years even then and arrived with the blue crystal just after he left.
Seven could have lived for a few centuries between "Survival" and the TV movie. His visible aging would support that. The same could be said for the interval between the movie and "The Night of the Doctor" in Eight's case.
The War Doctor must have fought in the Time War for a long time to have aged so much. He could have fought for 800 years for all we know and just refused to have counted those years after regenerating into Nine as his way of pretending that incarnation never existed.
There are plenty of situations where Ten has been travelling alone, like the time between Martha's departure and him picking up Donna, and the time between "The Waters of Mars" and "The End of Time" where we know Ten was involved in "Day of The Doctor". Ten could have been travelling for centuries on adventures we haven't seen.
The Doctor could really just be 1800 now, or 5000, or close to 10,000. I think he's probably between 1800 and 5000 years old which is easily old enough to lose track.
Three could have spent a few centuries traveling after his pardon from the Time Lords between Jo Grant's departure and Sarah Jane's arrival. Heck, he flew off alone to Metebelis 3 while Jo was still his companion. He could have been traveling for years even then and arrived with the blue crystal just after he left.
Seven could have lived for a few centuries between "Survival" and the TV movie. His visible aging would support that. The same could be said for the interval between the movie and "The Night of the Doctor" in Eight's case.
The War Doctor must have fought in the Time War for a long time to have aged so much. He could have fought for 800 years for all we know and just refused to have counted those years after regenerating into Nine as his way of pretending that incarnation never existed.
There are plenty of situations where Ten has been travelling alone, like the time between Martha's departure and him picking up Donna, and the time between "The Waters of Mars" and "The End of Time" where we know Ten was involved in "Day of The Doctor". Ten could have been travelling for centuries on adventures we haven't seen.
The Doctor could really just be 1800 now, or 5000, or close to 10,000. I think he's probably between 1800 and 5000 years old which is easily old enough to lose track.