We are one week away from my two year anniversary with League.
I miss the kick ass towers that really protected you, and made it easy to learn new champions without four strangers screaming at you. And I miss Yorick's original, hunchback look. He was my first main, and Undertaker my first skin, so it will probably always make me genuinely sad that he now looks like an aborted Metalocalypse character. (I like his new powers, it's just the old look I miss.)
Mostly, though, I like the many changes, or don't care one way or the other. They've done some killer reworks, like Warwick and Fiora, the quality of skins has steadily improved, they've made the jungle a lot more interesting, and I think their champion design continues to improve.
I can see burn out, though, too. I take two or three extended (2 to 4 week) breaks a year, and go play Heroes of the Storm (the minigolf of MOBAS!) to unwind. It's remarkably easy to get wrapped up in every little patch note around here, and stress all the fun straight out of the game.