10lbs a year seems low to me. I put on 10lbs in 4 months in football. Then again, I was being trained by one of the best staffs in the country. I'm at a fat 220 now, planning on going up to 230, the cutting to 215 by another hard training for 6-8 months and hopefully I'll be at my desired wieght and body fat %.
This is all natural too btw, genetics play a huge roll in it as well. But for the next 6-8 I'll be using supplements to help me out. (not illegal ones).