Through testing I have found my last keyboard before hitting the junkyard endured well over 3 million key taps. Pretty interesting if you think about it. That's a lot of punching of the keys. Keep in mind this keyboard that I am referring to, came and went in a years time. In result, this would mean I tap the keyboard almost 10,000 times per day. I just purchased my iMac G5 back in March along with a brand new Apple Keyboard and just in this short period of time, the A key is already discoloring. Also to keep in mind, it's not because of dirt simply because I wash my hands every time before I jump on my iMac (Yes, I love my Mac that much!).