I am not an expert, but I do have a high level of fitness. I too, LOVE Imax 3, especially the blasts...such a leg and butt burn!! I like to do Imax 3 about 2 times a week. It does include plyometrics (the blasts) so they can be very hard on your body. Obviously, I also include other Cathe cardio, such as DrillMax, Kick Max blast challenge, Imax 2 blasts, etc. I ussually create mish-moshes out of the premixes (DrillMax + Imax 3 blasts + BM2 power circuit + HSTA blasts. So my thought is that about 2 times a week is good depending on the other cardio you do. Too much can actually be harmful to your body..injury.
K