One year, I decided we just had to get to DHS to see Osborne Lights. So, we left Epcot WS, rushed over to BWV to grab a sweatshirt, then 'walked' to DHS. I made the entire trek, from the International Gateway to DHS turnstiles, in 18 mins. I was completely out of breath and close to dead, but I got there with about 10 mins to spare before DHS closed for the night. We were cranking though.
Normally, I would say it takes about 25 mins total. I do know that last Dec my friend and I were going to take the boat from the Intl Gateway to DHS, but it was just closing the doors and throwing off the lines. They joked with us when we told them we would beat them to DHS. We got to BW at about the same time...they may have beat us by about 30 seconds. But, since the boat had to then go to YC/BC, then S/D, before heading to DHS, we beat them. They were just coming around the bend in the canal as we got to bag check. But, we were walking at a fairly good clip...which the two of normally walk at.