How long should you wait to get micros after you get a relaxer?

Ok, so i'm wanting to get my hair done on the weekend of August 14th, and i currently have micro braids in. I wanted to get a relaxer and get more micros in, so they can be fresh for school.I hear that you have to wait three days after you get a relaxer to get braids back in, but i haven't really tried it. Also, I tried not getting my hair relaxer before and now my hair is so coarse that i can hear it crackling against the hair brush when i brush the front of it. So regardless, i'm getting new microbraids i just wanna know when is a good time to take them out, get a relaxer and put them back in. Thanks in advance :)