studied the language for five years

[Ashen Key]

According to the movie, the training for the actual Avatar Program MISSION is three years, and in a deleted scene Norm says that he studied the Na'vi language for five years (and he does have a PhD in xeno/anthropology, even if we don't know what he specialized in beyond the Na'vi).

So, do you guys think that those five years of language and three years of mission overlap, or is Norm referring to five years before the mission PLUS the three years mission time?

I can't work it out, and it's bugging me (also, rather important for massive backstory!fic *g*)