When I go once a week, there's not that much progress from week to week. Although when I skip a month altogether, it shows (I can barely breathe), so I guess even once a week is very good. BUT - I went 2x last week, and 3x the week before - and whoa. My body looked different! And it was easier, too, the 2nd class in the week definitely easier than the 1st. And I realized that it's ok to end sets short if I'm tired or use a lighter weight, the important thing is to show up at least 2 times a week. I'm going for 3.