keeping a steady level in my system, it really kept other things like fragmented sleep, cataplexy and muscle weakness under more control, so they did not snowball and all come back under, say, a little stress or something.
good luck. if you squirrel extra provigil away for a rainy day, the freezer or refrigerator in airtight containers might keep potency. but after years of fiddling with it, i find you should TAKE the fresh stuff, and not try to rotate leftovers.
that is, taking the most potent and effective drug as the scrip is refilled, is worth much more than storing the current prescription and using up left over pills first.
you rob yourself of some of the benefits and "normal" life you are trying to get back.