From my own experience, Do not mixed RAF. It sucks when you get a group going and Raf Falls off the first toon. All at once! If you have more than a week into RAF group A, play them to 60 many time, then start 2 more. In the meantime, make sure your computer will run 5 toons. I learned the hard way, in the middle of my RAF, my old beast would not handle it. Barely does now, until it crashes.

note:blue text is from my google spell checker