I would be inclined to think that 6-10 days may be a good starting point and may do the trick completely. My main experiences are with ephedrine, methylphenidate, and phenmetrazine at any great length and the tolerance build up was different for each drug. Since washing out tolerance essentially re-steepens the dose-response curve, potentiation with a chemically dissimilar stimulant can help to do the same thing afterwards so the tolerance slows down a bit next time.