EWL:
9 retreads is about right. Each time they get redone, they're NDTed for condition.
No nose wheel brakes on 737's (thank God!). As far as wear goes, you change 700 brakes about once every leap year. 800's are a bit quicker to wear. For what it's worth, NG brakes are substantially bigger than classic brakes.
Cheers
NAMD