The problem with some people is that they beceome 'stimlulant junkies'. I use to use epedra for about 1 ongoing year, bumping the dose whenever i gained a tolerance. This is a terribe cycle, because:
1 - no preworkout sup could give me a kick
2 - i couldn't gain a damn lb
3 - after a while i fell into a very seriouse overtrainning, whereby i lost over 10 lbs and was depressed for several months
I've learned that if you become completely dependent on stimulants, you exert more energy than your body can handle and in the end you are prone to injury or illness.
Right now i take 1 MQ PPA before i workout, which is only 4x /week to avoid gaining a tolerance