The loop i did was 4 days and i highly highly highly recommmend it. Start from China Basin trailhead, which is just a bit west of the Henry's Fork trailhead. Hike south to Red Castle Lake, Upper Red Castle Lake, etc. There is a small off-trail hike to the south from there, but it's not too hard. It put's you over a pass and then hooks up with a trail heading northeast towards King's Peak. From the peak you can head down the rockslide, xcountry a bit to Henry's Fork, and then follow the trails for a no-backtrack loop almost the entire way back to China Basin.