Mine was 6 minutes (normal), but I absued the Dare Devil and Survivor multipliers a lot to get the 100x multiplier achievement and 10 Dare Devils in one song (I think that's how you get the latter one). The only thing I don't like is when you get the two smaller bosses, and they come in from opposite corners: if they shoot the little circular, slow-moving death orbs, its quite annoying to try and see them with all the other lights.