About 15 minutes - but it you stroll along slow give it 20-25 minutes.
Very nice walk.
Stay on the path on the Dolphin side.
Make a left off the back entrance, before the boat docks.
Go past the Yatch Club on your left.
Then the SAB pool - fun to see.
Past the shipwreck (part of SAB).
Past the Lighthouse (Y/BC boat dock).
Past the Beach Club.
Then you are just a few feet from the EPCOT entrance - actually the World Showcase boat entrance - you come in around United Kingdom (on your left) and France on your right, across the foot bridge.
If World Showcase is not open (I think around 11 am) - then the CM's will let your walk by the countries to Future World.
Park tckets are checked at this entrance.
Stroller rentals and main information is where the bus/monorail entrance is located in World Showcase.
Do the same backwards to walk back from EPCOT's fireworks at night.
The path is well lit - the whole night.
One reason is the Boardwalk across the water from the Dolphin.
Many nightclubs are open late on the Boardwalk.
Also a great place to rent a bike, have an after dinner dessert or just walk around and burn off some calories from the day
If you are a pre-dawn riser, you will see CM's cleaning the paths, doing gardening, quietly mowing lawns, etc. Also the reasons for path lights to be on, all night.