Ecstasy can be detected via chemical tests to your urine, blood, salvia and hair. However, there is no certain period of time that is valid for everybody to say that it diminishes or stays. It depends on your body's chemical features and reaction to the substance. Roughly the time periods of detection can be accebted as: in blood 24 hours, in urine 24 to 72 hours, in salvia 48 hours and in a pin of hair in 6 months. However, MDMA is not detected with every simple test on your body. The tests must include some sort of an amphetamine examination. So basicly, the answer to your question in this manner is, yes the MDMA can be "detected" in your system in periods longer than 3 days from the time of consumption. However, you do not "feel" its presence in your system for 3 days.