I’ve been carrying a series of slightly-customized 3D printed bolt-type bladekeys since 2014. Despite being printed PLA, I’ve only had to print a new one once every several years – I wasn’t keeping good records but I think this is my third plastic body, second #8-32 “Chicago Binding Post,” and I upgraded the type of pocket clip at some point. I’m yet to have a catastrophic failure. The setup essentially eliminates key jingle, poking, or wear on pocket facings, while still being easy to tap check and use. The only slight downside to this setup is that when I attach a car key and put it in the vehicle, the blade-key dangles at knee height and occasionally grabs a leg hair – if I drove more I’d probably tweak how I attach the car key to fix that.
Pictures from the first one I carried in 2014, and the most recent swap out, induced by it “getting loose” and letting the stack of keys flip forward in my pocket – which turned out to be the result of several cracks in the plastic body. Plus, flexing that the bitting and labels are both obscured when closed, which I suppose is a minor security feature, especially when posting pictures on the Internet.
The first version I carried in 2014. IIRC that filament had greenish glow-in-the-dark additives. 
I think this one died from a drop onto concrete, cracks in the end. 
Old and new plastics. 
Extensive damage to the one I’ve been carrying for the last several years. 
A deeply grooved binding screw, plus a fresh one and the box, which probably represents a lifetime supply. 
My current iteration.
At this point I’d buy one of the fancy ones just to support the designer, but my desired size falls in between the models they do commercially (I use 15mm W x 58 L, closest sizes are 12mm W and 19mm W). Maybe sometime I’ll get ambitious and cut one in a different material on the router.
