clen says active around two days, if you take it 2-4 hours before you work out your peek plasma levels should be good for your work out and you should be fine for sleeping. people are diffrent but the only thing i get when i take clen is night sweats.
most ppl would say 30 is the lowest to take but ive done 25 a day and it did me fine you should take them on off days but a lower dose, say if your taking 40 mg's a day take 30 on an off day.