What I don't get is that if the Doctor was 800 yrs old when he was in his sixth life and he's now in his tenth incarnation. Shouldn't he be lebih like 1,000 to 1,100 yrs old?

simple he had to regerate alot between 6 and 10 he died faster. if anda think about it the first doctor would have been around for the longgest time because he would have been a kid and in relitivly little danger. there is no pre-set amount of tim per doctor

I think that he's lying ;)

O-kay thought of another. The Doctor's not in normal timeline. He jumps around a lot, so unless he's keeping a diary and saying I've just spent five days in New New York and one bulan with Shakespeare he's going to loose track of days. The Tardis would have to be keeping track of what time is appearing to pass. He can't just look at a calendar and say "Oh look, it's November 23rd again. Happy Birthday to me.!"