i'm going to contribute from my personal experiences and observations. this is not scientifically concrete, this is just personal experience. i've been rolling for 10 years and gone through cycles of varying levels of abuse and also cycles of responsible usage where i was more responsible. over the past few years i always dose pure mdma hcl so there's no question what i feel is from mdma and not other drugs, so that's a non-issue. i've dosed and redosed at many various intervals and i can honestly say that today i truly believe that the bit about dosing within a few hours seems to be true. i honestly believe that dosing 200mg at once is easier on your brain than dosing 100mg then another 100mg many hours later.
there's no denying that we all know there is a window where the "magic" happens, after that window closes then mdma becomes just another shitty stimulant. Ann Shulgin did work with this in therapeutic settings in the 1980's. The outcome of her research was that supplemental doses should be taken no later than 2 hours after the first dose is given.
Reference:
http://www.erowid.org/chemicals/mdma/mdma_info12.shtml
i have to agree with her 100% from my personal experience. now i'm going to share 2 experiences so we can compare and contrast redosing. you'll see that one of the examples is much different in the timeframe that a similar amount of mdma was administered (over 3 days) versus the other (over 3 weeks). the one where i went 3 days in a row had, expectedly, DRASTIC effects on my mood, tolerance, sleep regulation, you name it. when i dragged a similar amount of mdma over the course of 3 weeks it was much less exaggerated as when i did it all over 3 days. i'm irresponsible, i admit it. but some of this i did partially out of curiosity regarding tolerance and made myself a guinea pig.
i've rolled 3 weeks in a row recently (last month), prior to this i had not rolled in many months. all my doses were done within the first 2 hours of the experience. the first weekend i took 300mg, the second weekend i took 300mg, the third weekend i took 400mg. this definitely took its toll on me but i managed to get through work without any problems and while my emotions were definitely exaggerated, it wasn't too bad. i have a big tolerance to mdma so don't follow my examples please. i noticed a slight increase in tolerance over the course of the weeks but nothing too severe. i didn't have to "call in sick" to work and while i had anxiety, it was manageable. the last weekend i rolled was the 3rd weekend and that was 2 weeks ago. i'm still not completely baseline but i feel decent enough where i'm not having any anxiety problems anymore.
a little over a year ago i rolled 3 days in a row, prior to this i had not rolled in a few months. the first night i took 400mg, the second night i took 600mg, the third night i took 300mg. the first night i rolled very hard, the second night i rolled but it wasn't as good as the previous night, the third night i didn't roll at all. by that i mean my eyes did not dilate, my hunger was not suppressed, it just made me feel a really weird type of fucked up, not particularly euphoric and it gave me RLS. after this i had to call in sick to work for a week because the following week was absolute hell. i felt like i was constantly on a mild LSD come-up constantly, all the time, all day, every day for the first week. my emotions were completely out of whack. going down the street to the gas station was almost a bit much, everything was too strange and surreal feeling. forget about sleep. i would go to sleep and have a horrible nightmare, i'd wake up in a state of confusion not knowing if what just happened was real or not and to be honest, i would wake up terrified. i look at the clock and see it had only been 30-40 minutes or so. i would go back to sleep only to awake in another 30-50 minutes absolutely horrified from another nightmare. i didn't want to go back to sleep because i didn't want to have more nightmares. eventually i'd get so fatigued that i'd fall asleep to another nightmare. this is the horror of significant serotonin depletion. i would wake up sweating, scared shitless in a state of panic from the nightmares. after the first week i felt significantly better, after a couple weeks i felt decent enough to where it wasn't a concern. but it took me a few months before i felt back to 100%.
those are extreme examples but you can see that one of those examples definitely did much more damage than the other. aside from those 2 examples, i've dosed once then waited until coming down then dosed again (because i was out and dosed again when i got home). several times i've dosed all sorts of ways and it's my personal belief that the window of magic for dosing is within the first 2 hours. after that, the window of magic begins to decline IMHO. eventually, when the window is closed, mdma only exhibits its stimulant properties. this speaks volumes about serotonin. there is only a certain amount available for your roll and it is only available within a certain window of time. if you continue dosing past that window or over that amount, then the primary effect of mdma is that of a dopamine agonist. remember where mdma neurotoxicity comes into play, the more dopamine that is released during an mdma session the more neurotoxicity becomes prevalent. i can vouch for just how destructive this neurotoxicity can be, you can do some real damage if you're not careful with your dosing and the frequency. my words of advice is to not do it more than once per month and when you do it, to stick with Ann Shulgins dosing schedule.
i hope the experiences i shared and everything i've put my poor brain through result in some information that is valuable to somebody.
take care
