Man i have tripped 3 days in a row, waited 2 days then tripped 2 times in 2 days after that.
Tolerance is simply a guideline, "your tolerance will go up with use" just means you need to take moar.
Ive actually had this situation, take 1 and not get really anything, the next day i took 2-3 i think of the same tabs and tripped fairly hard. Was weird, as if just doing one on its own didnt hit threshhold.