I don't think it's going to affect the duration much. Though I've had rolls end abruptly because the music stopped. It's just going to be a different roll, more energetic
What I would do is just go all out one night man. If you keep it to one night you can redose a bit and keep it going the entire night. That's IMO the only way to extend the roll. Take it from one of the many who regret abusing MDMA, it really isn't worth it that one night of extra fun when you roll on back to back days. It will in the long run completely ruin the experience. Not even in the long run, the way you're using it's going to be sooner rather than later
That being said I have a feeling you're going to do it anyways, against advice, as I stupidly did once. So following is a bit of advice for when you do decide to be stupid. Please reconsider, take MDMA one day and do other drugs the other days. Or at the very least only do two days, not three. But anyways, in the spirit of harm reduction here is some advice. If you are really dead set on rolling multiple days, be smart:
-Eat enough & Sleep plenty beforehand, during and after
-Don't mix it with any other substance, not even alcohol (apart from maybe weed if you're used to smoking it) this is important, a very big part of long-term comedown cases we see here involve other drugs
-take a very very long break afterwards. At least 3 months I would say. Rolling back to back days will create tolerance. For me it even created permanent tolerance after rolling for 3 days in a row only once, I regret it a lot now
-Keep your doses normal and avoid redosing at all costs. Redosing + rolling back to back days is a recipe for a bad and long comedown
-Look into pre- and postloading and apply these to your daily regimen to decrease the amount of damage you do to your body
-Make sure you test your MDMA with a testkit
-Drink enough but not too much (0.5l each hour in sips when dancing should do it, if you aren't dancing just drink your usual quantity)
-If it isn't an outside festival go cool down once in a while if you are dancing hard. Damage because of hyperthermia is not easily done but it is possible
-Listen to your body, you know it best, if it gives you cues listen to them
-Be safe and have fun, in case I didn't say it before: don't roll back to back days
