I was more thinking for "long-term" energy boost to enable goal as well as fat burning I would use Caffeine/ephedrine for 2-3 weeks , then go to caffeine/Yohimbine ,
If I am already exhausted Yohimbine doesn't provide much in way of help keeping myself awake, but i try and take it first thing in a.m and around lunch , no later ... caffeine doesn't effect my ability to go to sleep and for awhile I wouldn't take ephedrine past 3-4 if going to bed around 8-9 , just to be safe but for me I usually can take it up to close to bed , especially if I have a late workout the. I'll take it before regardless of time as I use the energy