I change up my rotation seasonally or monthly. When I get a new system or series, I'll go through a rotation of that until it's done. I sometimes loosely plan different days of the week for different modalities. Now that the weather is finally starting to get warmer, though, I'm likely to eschew my DVDs for a few months and try to fit in as many long jogging sessions outside as I can, going back to DVDs on days the weather isn't cooperating. I've been cooped up inside way too long (as have we all!) and without my trips to the local yoga studio to break up at-home workouts, I have GOT to get outside.