I nicknamed back in Red version, but it was typically absolute nonsense, like garbles of letters and numbers. The coherent names were hilarious to rediscover, though. My first Venusaur was named BIGPLATE (I think I was trying to say Big Plant), my second Venusaur was named Pinsir (the only Pokemon on the entire cart with proper capitalization), and my Golem was named STROUGMAN.
I completely stopped with nicknames from Silver all the way to Diamond. I'll never know why.
And then starting with SoulSilver I nickname every single thing that'll see battle, even utility Pokemon like my Horde EV Tropius. I use references because I'm lame.
SoulSilver was also the game where I stopped using my own name as the trainer's name. When did other anons stop using their real names, if ever?