As for keyboards I actually bought myself, the Monoprice 9433 I'm typing this on was the first.
Heh, I've only actually had 6 keyboards used on a regular basis before this one, and most weren't mine, they were my parents' until they got passed on to me.

Let's see, the keyboard on my dad's 286 back in the 90s, the one that came with my mom's HP with 233MHz Pentium, the one that came with her HP with 900MHz Athlon, the one that came with the Sony with the 2.8GHz Pentium 4, the replacement after a cat knocked water onto it, the one that came with the Acer my dad got me... We never got new computers much(I inherit the old ones generally), and we've never gone through keyboards. (Yeah there's a lot of gap between dad's 286 and my mom finally getting a computer in '97, I'm not counting laptops here, I've never been able to stand using them.)