Ryan sez, "We have a medical transcriptionist on staff who has been using the same keyboard for the last 8.5 years. My co-worker replaced it yesterday, and when he first showed it to me I thought someone had taken a blowtorch to it! The most frequently used keys have been completely worn through, exposing the mechanism beneath. Zoom in and check out the indentation on the Backspace key! The keyboard still works fine, so there's something to be said for durability. BTW, it's a NMB Technologies model RT2358TW."
Some people are hard on keyboards — I tend the blow the contacts on the left side of the board really fast, knocking out the Ctrl, Alt and left side of the spacebar. Charlie Stross's keyboards lose their lettering in mere months, and my pal Seth Schoen types like a machinegun, but I've never noticed any particular wear on his keyboards.