So, yes there are benefits but it really does depend on what style you are going for. If you leave a mash at about 152 for 4h you will break down almost all of the sugars, carbs etc, into things that can be fermented. If you do it at 162 you will most likely also get all of the sugars etc into ferment-ables as well. This also happens after about 1h at 152, 4h wouldn't get you much if any more and kill the body etc which requires the dexitrins to give mouth feel. Conversion rates occur at different times for different grains. Adjuncts don't typically add any sugar at all that CAN be fermented so seeping them longer doesn't do anything. Most grains will actually convert at about 45min, some as short as 15 (American 6-row does in fact convert completely in 15min), it all depends on how many enzymes are in the barley.
A 4h mash will not hurt anything but you can't really gain anything by going that long. The problem that I would think of is temp control and if it drops you have the chance to get bacteria in your cooler which then dies in the boil... so no real harm there.