I only have conclusive data on 7 players that I know I played every week at the same position. All of them took exactly 11 weeks to gain .5 BPOS, and their talent levels were: two 4*, two 3.5*, one 3* and two 2.5*. I know this is a small sample set, but it is curious that they all gained BPOS at the same rate.

I only have 3.5, 4, 4.5, and 5* talent players, but so far, every one of them have increased .5* of BPOS for every 10 games played at a given position, regardless of position.

I've been tracking using Excel. Some have trained 10 straight games from their previous increase, some trained a few games here and there or switched positions for a few games. But regardless of how or where they played, if they played the same position for 10 games (straight or not) they increased by .5* BPOS. I'm still collecting more data. I won't be checking any players lower than 3.5* talent for this though.