I'm really starting to be seriously annoyed with those wooden Knitpicks circs. Not only are their colours something of a hindrance to knitting in darker yarns (I tried them with fine black silk and quickly gave up because the yarn was simply not visible against the dark shafts of the needles) but it also seems as though your average set won't outlast the knitting of a sweater. At least not in the hands of the Yarn Owl... and those hands are not the roughest ones around.
My pre-Christmas knitting project was a top-down raglan sweater in Malabrigo sockyarn, knitted on 3mm circs. Yes, wooden Knitpicks. In the case of this particular set, it would seem that the different coloured layers of wood aren't all equally hard, because well before the sweater was finished the light-coloured layer on the one tip had visibly worn down while its adjacent, and darker, layer had not, resulting in a knife-edge projection that was painfully sharp to the touch, snagged on the yarn at every stitch, and left scratches on the other needle.
I fixed that for the time being by smoothing the tip down with a glass nail file and then polishing it with Micromesh. This morning's mishap, though, will be less easy to repair.
The current project is another top-down raglan, this time in black cashmere that's slightly finer than sockyarn and hence being worked on 2.5mm circs. I'm most of the way down the body at this point and there has been no sign of tip erosion so far (there are also no layers of pale wood forming the tips of this set), but earlier today the right needle just snapped in two in my hand about 5cm down from the tip. (And no, I had not tightened my fist on it; I was just knitting normally.) I ended up having to disentangle the equivalent of a shattered toothpick from my cashmere yarn and hunting for another needle to retrieve my dropped stitches.
The needle was almost new. I might have used it for a couple of pairs of socks before this sweater, but not much more than that. The 3mm one with the eroded tip was fresh out of the original wrapper when I started the sockyarn sweater, so on balance I am not impressed. Last autumn I bought quite a large number of wooden Knitpicks in all the sizes I use regularly, and even not so regularly. Now I wish I'd gone for the metal ones... because if these two are an example of the life expectancy of the wooden ones, the investment was not a particularly wise one.