Just FYI the schedules can change at a moment's notice. I just went on the USO tour during the end of Jan and the Dorasan station and 3rd infiltration tunnel parts of the tour were cancelled due to "security and weather" reasons. There was maybe 1cm on snow on the ground max. The JSA part thankfully didn't get cancelled.

They replaced it with a tour of some other observatory that had a great view and Imjingak Park to fill the time before the JSA.

Just FYI the bulgogi they serve is not great and not worth the 10,000 won they charge. It's some soupy mess that's served in what resembles a high school cafeteria. If for some reason they change the schedule on you last minute and take you to Imjingak Park, I suggest eating there. There's a Popeye's and a Korean restaurant there. You are also allowed to bring your own food as well and eat with everyone else who is having the Bulgogi lunch.