Last a long time...? I'm not so sure. See, the carbon and resin composites aren't really that wear resistant, it's just super-amazing in tension. The weave makes it good in tension in multiple directions, so i you dropped them, they likely wouldn't break. I suspect we'd wear through the resin like normal plastic (Depending on what was used).
Now what would last a really long time: ceramic keycaps. I want to get an oven (or overvolt a toaster) and DIY some AL2O3 (alumina) keycaps. You can keep the temperature relatively "low" by sintering for a long time. Unfortunately, I still need an oven that can do 800C or higher.