Well, our standard session go longer than that!We begin play at around 6 pm eastern and play until anywhere from 2-4 am.
We start at about 4pm and play until about 2-6 am. We don't continue playing the next morning, though.
Back in the days we'd tried to play a marathon session, starting at 8am but it unfortunately ended with a tpk before noon.
Last year most of my regular D&D group spent a week in a Center Park, giving 4e a test run. Since everyone enjoyed it, we're repeating it this year, continuing the adventure. The individual sessions weren't as long as our regular ones, though.