You never had anything like this happen to you?
This is the extreme, obviously the wrong rope for the job of split tail, but eventually all split tails burn or glaze to the point they have to be replaced. And, I never took a ride down more then 50 feet that I didn't have to nurse the split tail a little - it either gets too hot or jams up or both. I've tried most ropes from Tenex to Beeline to Stay Set and most knots from Blakes to Knut to VT to Martin. They all need at least a little attention on a long ride down.
Nope, at least not that bad. That's more a split tail failure than a knot failure. Have burned many split tails but never that bad. I've got to honest with you, i really have no problems with my friction hitches, even with my extreme weight and long descents. I've spent hours in a tree without ever having to dress my martin. In fact one of my tests when i was switching over to the martin was dropping straight out of a tree 90 feet up. Sure, you can't burn out of a tree with it but slow and steady will get you down without a problem.
My descenders (Petzl STOP, I'D, or Figure 8) dissipate the heat better and give me a smooth, quick, hassle free ride. I back them up with a martin hitch on my side D, but I have never had a reason to worry about them. Then there are just times when SRT and mechanical are more efficient than DdRT, although at my age I am a big proponent of the mechanical advantage of DdRT.
Interesting, the mechanical descenders are perfectly safe, yet you back them up anyway? I have never backed up a friction hitch.
I'll tell you the real reason i don't use any mechanical descender-i have seen them fail, and fail badly, on frozen ropes. Now sure, this is a bit extreme and most climbers will never have to deal with this problem. But around here, for a good chunk of the year, this is a regular problem. I expect my equipment to work no matter the weather or conditions-mechanical descenders don't seem to have what it takes whereas my friction hitches have never let me down even over twelve years and every kind of condition imaginable. (By frozen rope i don't mean a cold rope but one that has gotten soaked and then has froze.)