It may depend on the time of year. We always go during the summer, when the resorts are full and the crowds are pretty high. So they run the busses a lot. We rarely have over a 20 minute wait for a bus at VWL, though many have commented that they have experienced slower.
Disney tells us to allow an hour to get to a destination on the bus. In our experience, we've rarely come even close to that.
The one exception is DAK, but that's because it's on the far side of the property, and they always stop at Blizzard Beach on the way there and back.