IF there is not traffic blocking the way, the bus trip (after a bus comes for you) to the MK from BC is only 10 minutes. It is true that the wait for the bus varies -- and can be in excess of 20 minutes, but that is not common.
The trip back to YC/BC from MK is slightly longer as it is not simply a reverse route, and has to go by the Poly and TTC road.
AK bus route is shorter -- but often/usually you also stop at Blizzard Beach on the way to AK and the way back, making it longer.