I think george is wrong if he says 2 days on, 2 days off stops the clen from downgrading your receptors. The 2 on 2 off schedule is simply because clen's half life is something like 36-48 hours, so this keeps your blood levels even. You will still need to take 2 weeks off after 18 days of usage if you want to avoid receptor downgrade.
I use clen post cycle as an anti-catabolic and when I am dieting -but again only as an anti-catabolic. I feel its impact on your body doesn't justify its use simply to burn and extra 200-300 cals a day. It is simple to reduce your dietary intake by 200-300 calories. If you do use clen for dieting then you should stack it with t3 to make it worthwhile.