Genghis - We've had to land the B-1 a couple of times with the wing swept full back (67.5 deg). It's not pretty but can be done. Approach speed, lightweight, is 250k (which is also the tire limit). Of course, the tires go, and the brakes catch fire, but usually very little damage. Pretty exciting though, they say.
BTW, the engineers told us pilots early in the program, that, due to the redundant design, it was impossible for the wings to get stuck back. Yea, right, we said --You don't know how many clever and devious ways pilots have to break airplanes. How many times have you heard that one from a design engineer? Cheers.