I usually only do one roleplay at a time...and one that I've created and decided to host. This is largely due to my inability to focus on more than one thing at a time. There are exceptions, of course, as I can juggle the RP I'm GMing (which is always in advanced, due to the standard 'speed' of the threads and my own posting expectations) and something like a high-casual or low-advanced 1x1.