According to google maps the walk from Two River's Park to Office Depot is 2.8 miles, so 5.6 round trip. I did chat with a coworker at Office Depot for about 40 minutes so it wasn't all in one go but still a decent walk all done in under 3 hours, it took me about 50 minutes to walk each way. It was a very easy pleasant walk.
Compare that to a walk I went on when I first was looking for a place to stay in Glenwood. I walked from the hotel I was staying at to downtown Glenwood and back. According to google maps thats 2.2 miles. By the time I got back to my hotel I wasn't doing too well. Breathing was pretty hard, my legs were burning, all in all not doing too well.
I'm not sure how much of that has to do with exercise and how much has to do with getting used to the air. I wasn't exactly sedentary in Kansas, especially by Kansas standards. Hikes and kayaking were both reasonably common activities for me. Either way though it feels great to finish a walk like that and not even notice that I was on one.