Two regenerations. Twelve hundred years.
Let me repeat that. Two regenerations. Twelve hundred years. That's how long, for the Doctor, give or take a decade or so, was between meeting Caecilius and his family and his new regeneration cycle on Trenzalore.
Twelve. Hundred. Years.
It would have made more sense if the Doctor subconsciously took the form of someone on Trenzalore. After all, he'd seen everyone there, for nine hundred years, be born, grow old, and die. He lived with them daily in a way that he never lived with Clara.
Sometimes I think Moffat forgets that marooned the Doctor on Trenzalore for hundreds of years, because the twelfth Doctor never acts like it. His relationship with Clara, for one thing, has never felt like it has that kind of discontinuity in it; he picks up in "Deep Breath" like the Christmas dinner with her family was a few days previous.
This explanation is like the fourth wall breakage last week. It's something meta that makes sense in terms of television and its production, but it makes zero sense in-universe. None.
Twelve hundred years, Moffat! Twelve. Hundred. Years.