I've seen a number of speed vendors state that dry speed will not be as fresh or stay as potent as wet speed. They say its meant to be wet and drying it all out is the wrong way to handle it.
I know that could very well be a marketing ploy, but maybe there is some truth to it?
Does anyone know anything about the credibility of this?
Completely incorrect. Amphetamine sulfate is very stable. In fact reducing water content typically makes drugs MORE stable, not less.