I used a pair of them for 2 1/2 years without a problem, other than the twist lock. But I have never been convinced they help, actually I think they slow me down. But they do work well as poles for shelters.
Last fall I broke both of them in one day, on a long 9,000 foot descent that I was not really in shape to do. My legs got very wobbly towards the end. They broke trying to support my weight when I put too much lateral weight, which I know will break them. I really think that had I gone down without them, my legs would have not gotten as tired, because they induce you to change your natural posture... or maybe I don't know how to use them properly.
So for the past few months I have been hiking without poles at all, and have been much happier. I did get a pair of carbon fiber Black Diamond poles for snowshoeing, because of the superior locking system. I took these on a desert mountain cross country trip towards the end of last year to try them out on some of the more difficult ascents and descents. Ended up leaving them strapped to my pack the whole time, and was happier not using them at all.
So now I have 4 pieces of LT4 poles. GG sells the bottom sections separately and I haven't yet decided if I will replace them yet. The breakage was due to applying pressure that they are not designed to handle.
I may even dig out my old hiking staff, I like it better anyway.