Great response on the pros and cons of the Theta LT versus MEC Flight pants, by the way. But what about a pair with a heavy-duty rear-end that will withstand glissading? I've yet to find anything adequate, so tend to slide down on my emergency blanket to save my expensive Gore-Tex pants. Don Tacoma, Washington
But of course, it was also murder on pants, especially in "corn-snow" conditions when you were basically sliding on little ice crystals. Once upon a time that was less of an issue because the only waterproof pants available were inexpensive coated-nylon pants. So if you wore a hole in the butt, it was no big deal. But when you pay $300 for a pair of high-end Gore-Tex pants, you probably don't want to trash them.
While I don't want to preach, you might also consider working on your standing glissade. Safer, reallythere have been lots of cases where sitting glissaders tumbled forwards and whacked into trees or rocks. Not quite as much fun as that long, sitting slide, but equally satisfying.