it may depend on what specialty you're applying to. i am applting to pathology and i have been told by a program that they want me to interview well before january because they like to have made their decisions by then.
this is not all of the programs, however, as some of them do offer interviews in january.
apparently, it is a known fact that pathology likes to interview earlier than other specialties....that has been the word on the street and i am finding it to be true now that i am in the process of applying.
so, i suggest that you find out what the trend is for your specialty and especially for the programs you are very interested in...you might even ask them directly if you are truly that concerned.
i would imagine that for soemthing like IM or Peds or IM, interviews can go into feburary since they really need to fill a lot of spots.
in all honesty, i would think if they offer you a date in january, then you should be considered with the same seriousness as those who interviewed in novemeber.
ultimately, if you're good and they want you, they'll take you no matter when you interview.