Well, let’s see…. Forever! When you relax your hair the process is permanent. The relaxer causes permanent change to your natural hair. It destroys a big portion of the chemicals that give the wavy shape to your natural hair. Those hair chemicals (produced by the body) also provide strength to your natural hair. If you want to go natural you will have to either slowly transition to natural hair, or do the big chop.
Your hair grows 1/2 an inch on average every month. If you do not want to do the big chop, the best thing you can do is to let your hair grow for at least 12 to 18 months, then remove the relaxed part of your hair. I transitioned for 8 or 9 months before I removed the relaxed part of my hair. I recommend that you talk to your hair stylist to discuss your options. You can opt for different protective styles like wigs, braids, or weave if you don’t want to deal with two textured hair all the time, as two textured hair requires more care and patience.