I have not seen the new "extended wear" knives. The standard ones are wore out in about 800 acres of beans. I have been going to experiment with putting a hard surface of some kind on a set and see what happens but never get around to it. I hate flipping them around or putting in new every year. No way over tightening has them locked down. Every time I flip or change mine I will get at least one with the piece that goes in the mount out of whack and it will be locked down when I tighten it but obviously catch that as soon as I get it tight and correct the mistake. For all of them to be locked down you had to put something together wrong on all of them or there is an issue with the bushing etc.. causing them to not fit correctly. Over tightening isn't the problem I would almost guarantee. .