Do full day conferences really have much benefit, or is it better to do half day work, half day play

Do delegates suffer from informtation overload when they must sit through a full 7 - 9 hour working conference, or will the message be made more potent by shortening the work part of the day and adding a play part to the day. By play I mean "adventure experience" or visit the elephant sanctuary, or learn to snow ski or taking a hot air ballon ride, or getting a seat in a race car etc etc etc.