I honestly still love my Ducky Shine 3 Yellow with Cherry Blues, it feels just as responsive and clicky as the first day I started typing on it, it's light dancing LED's were also really neat to me at the time. (My how times have changed, one color LED's are boring now, everything is moving rainbows.)
I've used it for around 4 years now, going on 5 in the new year here. I don't honestly believe I'll ever get rid of it, plus I was originally drawn by it's color, I had made a themed desktop back in the day that was all yellow and black, and that was my crown jewel.
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If the time doesn't have to be contiguous, then I did use a Model M as a kid for a few years on a PS/2 30, and I adored it, when I bought my first one in adulthood a year back, it was like coming home for me. I will always adore buckling springs, and have since grown my collection to be overwhelmingly that. I'll probably have one as my primary keyboard for the rest of my life if my care of them has anything to say about it.