bpt,
It takes me about 2 hours. I walk at a pace of 2-2.5 miles per hour, depending on a variety of factors. I usually take a rest on Ocean Parkway and eat my dessert- a container of pineapple or honeydew and a bottle of water- and then continue walking.
I once walked from Caesar’s Bay to 18th and Ocean Parkway and back, and it took a little more than 3 hours.
I like this better than the gym, and best of all, it’s free, and I get to do my best thinking while walking.