I was having the same thoughts. So I only do it x2-3 a week. Good thing I saw this post, too, I traded out 30 day shred for ab bootcamp, and almost forgot to do it this week.
It gets easier, but I don't know if it really matters about the cardio because it's only like, three minutes, three times. So really that's only like 10 minutes when you put it all together. But if you aren't comfortable doing it, then that's fine. I've seen results with just x3 a week.