Okay that seems fairly clear cut. There is no evidence so far thatloses its power following regular use.
In theory it should do, 'cause there's always tolerance around dopamine ... BUT it is said that some dopamine 'stimulants' never loose their effectiveness but do weaken. might be in that camp.
I've a USP stack in the post so we'll see how it runs. I think - but I have no evidence - that I struggle with deep sleep. If so then PowerFull should have a bigger impact.