How long should I wait to bleach my hair again?

I while back I dyed my hair deep burgundy by Revlon. It faded a bit and I had about an inch of roots showing. I'm trying to bleach it blonde so I can "start fresh." I can see that my roots are becoming blonder than the rest of my hair. How long should I wait to bleach it again (Using Revlon)? I know I'm probably going to have to bleach it twice. How long should I wait to bleach it again. Thanks.