I would wait a while longer to be safe. Half-life is not always a good indication. For instance, if you've been on an SSRI anti-depressant for a very long time, you would think that a week or so after quitting you should be able to roll again judging by the half-life. However, this is not the case, it can sometimes take multiple weeks or in rare cases months even for the full effects of MDMA to be felt again as evidenced by reports encountered over the years. Some anti-depressants have long-lasting effects, much longer than the half-life would indicate. You should not take chances with something like that
*edit*
I didn't see this was such an old thread that simstim was replying to before I posted. Nevertheless I'll leave this reply up in case someone else has the same question