* max 1.5mg/kg, max 0.5mg/kg redose after an hour and a half according to Dr. Alexander Shulgin in his book PiHKAL (Phenethylamines i Have Known And Loved)
Dancesafe.org, rollsafe.org, and the "godfather of ecstasy", Dr. Alexander Shulgin all agree on 90 days. Dr. Shulgin is famous for personally testing hundreds of psychoactive drugs (mostly ones he invented) and authoring PiHKAL and TiHKAL, books describing 234 drugs with "detailed synthesis instructions, bioassays, dosages, and other commentary". (Wikipedia) He's both a professional drug user and a professional drug researcher. In his own more poetic words, he said to reserve MDMA use to "once a season". Shulgin began the initial research on MDMA as a therapeutic and recreational drug in the 1960s. His work reflects decades of research on human subjects, himself included. I'd say he's one of the most qualified experts on MDMA.