Not more than 2 pills
I consider myself a fairly average pill user with not a low tolerance and not an exceptionally high tolerance. I also find myself reacting to MDMA and MDA by the text book. Therefore, I consider myself a fairly generic for most people judge of effects. I have found when taking clean MDMA, a 3rd dose does absolutelly fuck all or very very little. Only when MDA comes into picture I can take more than 2 pills and feel the near full effects of every pill, perhas by interchanging MDMA and MDA pill or taking mixed MDMA and MDA pills. This is of course because MDA and MDMA are not cross tolerant.
As an example, as many have, I found the recent blue gatecrashers to be very very clean MDMA with no MDA and fairly ok does of MDMA. I'd say around 90mg - 100mg. The first one was excellent, the second was ok but pretty weak, and the third one did jack shit and was an utter waste of money. Then a half of an MDA pill I can't remember kicked in and in terms of strength was on the level of the first gatecrasher.