I try to have at least a months break between each event, more like 2 during uni. This keeps me sane and minimises the chance of me building up a tolerance.
If the event includes a really big international DJ, like Lawler recently or Carl Cox - ill have about 2 or 2.5 in a night. This will usually keep me chopped for about 7 hours, but i tend to eat 1.5 to 2 of those pills in the first 1.5 hours of the night (i love getting hit hard!). At lawler the other night had 3/4 of a BB at 11:45 then a HQ at 12:45 - this was a superb combo, and didnt need to eat again until 4:00am (i had 3/4 a BB to see out the morning).
On a normal night out ill have 1 good pill in halves, spaced out over the night. No need to always overdo it.
Usually 4 big nights a year, and 10 smaller ones (maybe more actually...)
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