In Doctor Who, season 6, we find out some more information regarding how Time Lords age. One of which is that Melody Pond (River Song) grew up alongside her mother and father and ages at the same rate as a normal human, but we could account this to her being half human.
Earlier in the same season (Episode 1, Season 6), we see The Doctor at age 1103, 195 years older than the last time Rory and Amy saw him (at the age of 908) suggesting that a full-Time Lord can physically not age. But if we look at older episodes such as Season 3, Episode 13, The Master ages the doctor by 100 years and his physical appearance changes.
Do Time Lords physically age depending on certain factors such as they age 1 year for every 10 human years for example, or are there other factors in play?