I remember when I came off my P90X rotation, my endurance was awful! So, for the next month I did a rotation that was more endurance based. Here is an example of what I did:
M: circuit
T: cardio interval
W: full body weight endurance
Th: run for 45-60 min
F: circuit
S: cardio steady state
Su: yoga or rest
Then after a month, I switched back to more concentration on strength with a 3 day split and 4 days of cardio, with yoga or rest on Sunday.
I've continued to do this and don't think that I've lost my P90X strength and really think I'm more in shape by mixing it up more. But I will say that for the past 4 months, I've been following Cathe's monthly rotations and I'm really enjoying doing this (I think she does a great job mixing it up each month!).
HTH's
Becky