bankroll management

[jsnipes28]

i started playing 200NL cause i kept getting hassled by me friend and my ego couldnt take it. so i played and got lucky and pushed my bankroll to about 800. then i figured i should be safe and play 100Nl. I've been winning consistently and have regularly cashed out so that my br reads about 700 +-60. How much should i increase my br before i move to 200. What is a safe number, 5-10 buy-ins?