To be honest, I use it at every wash and it seems to keep my hair from breaking. I have a lot less hair in the sink, floor and in my comb since using this weekly. This is how I use it:
1. wash w/poo
2. rinse with rinse (lol)
3. put in aphogee 2 min. reconstructor, cover with plastic cap and let sit 5 minutes
4. put in deep conditioner and sit under dryer
I think you should have no problems using it while you have cornrows. I think you won't have a lot of breakage either when you take out your braids.