Snurk must walk faster than us! It depends on where you are in Future World, of course, but I think 10 minutes would be an absolute minimum and that's walking briskly. I would allow 20 minutes, most of which will be spent walking through Epcot to the International Gateway entrance.
But if walking is an issue, you can pick up the boat at the International Gateway and get off on the Boardwalk. It takes much longer than walking but is a nice ride and you can avoid the walk if that is necessary.