I was under the impression that the east-coast Gukto Jongju running from the Unification Observatory by the eastern end of the DMZ all the way down to Busan (presumably to the selfsame Nakdong River Barrage where the Four Rivers trail culminates) was 720 kilometers long. Based on my calculations, though, the trail is only 610 km long, making it 23 km shorter than the Four Rivers trail. I'm guessing this is because the path I plotted doesn't follow the actual trail all that precisely. Naver Map doesn't (yet) have a setting where you can type in "follow the official bike trail only," so I had to figure my way down to Busan on my own. I don't think I took too many shortcuts, but the result is still a disappointingly short trail. Check out my route for yourself and tell me where I went wrong. Meanwhile, I'm going to check some other sources that had been given to me by online acquaintances to see how I might re-plot the route so that it conforms more closely to the official Gukto Jongju.
One thing I know for sure, though: there really are so many motels, resort hotels, minbak, and pensions along the way that the need for camping will be zero. In other words: I can do the entire walk without once having to camp. Upshot: no backpack necessary, which means I'll be able to walk relatively fast each day. The average length of each segment is a bit under 24 km, which means each day—with only one or two exceptions—will be a fairly easy march. Right now, the walk is looking as though it'll take only 26 days. If I am able to re-plot the walk more properly so that it comes out closer to 720 km, that'll add another 4 or so days to the total walk. That's about what I'd been expecting, which is why my current calculation of the walk's distance comes as a surprise. I'll see about rechecking the distance over the next week or so. Meantime, feel free to leave comments.