As we enter our slow season, the Swan & Dolphin will be combined with the rest of the Epcot resorts during normal operation hours. Downtown Disney will still run a dedicated Boardwalk bus between 6:30pm and 11:30pm. All other times, they will be combined.
The complete cycle... from MK to S/D/Y/B/BW, and back to MK is approx 40 minutes. This can usually be done in less than 35 minutes. (And yes, by obeying all traffic laws.) With a 35 min cycle, it takes 13 minutes to get to the Swan. Probably about 20 mins for the Boardwalk. Then another 13 minutes to get back to the MK. So on-board time would be 13-20 minutes for the MK.
As for frequency... MK busses have gotten to the point with Flex Dispatch that we're running every 11-12 minutes. In the morning, the busses are dispatched via MOD from the Studios parking lot. Their routes may vary... for example, Swan, Dolphin, Boardwalk. It's just based on demand.
Downtown Disney... that's another matter altogether. Somedays its fine... other days... it's hit or miss. During peak times, anticipate the Downtown busses to be running behind schedule.