I have on the 5/10 6-Max haven't played as many hands as you but I've played 12,000 and have an average of 6.??bb/100. The biggest difference once you start moving up is to learn how to control the betting more. This leads you to having more information on your opponent. It is often pretty easy to make reads on players at this level and you should be able to save a few bets on the river. Secondly you need a pretty decent size bankroll at least $5,000 if you want to be playing the 5/10. I played short for about a year and it cost me dearly a few times.