I never really quit explicitly, but around halfway the third gen, I sort of started slipping away from the episodes, and I hardly played the newer games. I wasn't really acquainted with the fandom any longer and hardly even knew the names of any of the third gen pokémon. I guess it happened when my time was occupied with school, because at the time, I entered high school, but even before that, in my last two years of primary -- just after I moved to Tilburg -- I started getting out of touch with pokémon. I guess most of my classmates got me discouraged from watching and playing pokémon because I was teased about it. They found me infantile for liking it and I was sort of proselytised to act more like them, like one of those "gangsta" 11 year olds, if you get the drift. To be honest, I never really liked that school, and they even tried to convince me to go to a much lower quality high school afterwards because it would be more "fun" there. That's when I decided to hell with them, and I turned my back on my class.
That's to give you the backstory of why my love for pokémon began to fade. Kind of like a poor kid who was missing an identity, I am pretty sure I've been a Yoshi fanboy, then I went through a period I was obsessed with moose (don't ask), then one insuspicious afternoon, I was surfing the web, and I am not sure what the heck I searched for, but for some reason, a blue jackal showed up on my screen in one of the results, and it piqued my interest so much that I wanted to know what it was from. I wasn't really sure. It could have been a digimon, it could have been from some obscure but probably awesome cartoon I didn't know about. I eventually got a hunch that it was a pokémon, and sure enough, when I searched all over bulbapedia I found that blue jackal named Lucario again, and I re-discovered pokémon.
My absence has still left a big gap for me. A big chunk of the third generation, and almost all of the fourth generation anime is just a big question mark for me. I rarely even watch fifth generation because of how bad I think it is, but the games, that's where I am back, that and the roleplaying. I've sort of gotten to that point where I think the fan-created content has become more interesting than the actual franchise, but forget pokémon I will never again.