Skiman
Super Freak
Is there a reason why you (or people in general) change brands?? Does cinstantly changing boost up muscle gain or something?? Just asking.
There's only a tolerance, I'd say it's best to get on 3 months and then get off and cycle it off again so your body is not dependent on the supplement.
Their main ingredient in these that pushes us is caffeine and all the amino acids, so it's pretty easy to make your own pre workout drink without going this route.
It's all different mg of caffeine a certain individual has a tolerance to is all.