Back when I was in Middle School, I couldn't get enough of the game. I was actually one of the few members that weren't total idiots.
One of my favorite things of the game was that everyone had an opportunity to get currency, no matter what level you were. You could be level 3, just mining, and you'd be able to make money. There were also many ways to make money.
Anyway, I had about 4 accounts total, got one to about level 83, got a stuffload of money and the best weapon in the game, then got bored of it. As the updates started to get less original and more idiotic to please their community, I started to repel away from the game until I just randomly quit one day.
The very last time I played the game is when they added better animations for a few things, and spruced up one of the major cities in the game.
Anyhow, for tl;dr'ers, I played until I got a med-high level, got bored, and then quit. Great game though, and I miss the way it used to be back when the community was intelligible, and the game was cleaner, and had less pointless updates.
One last thing. I'm tired of hearing how people say "I want to stop playing but, I'm addicted to it/I can't stop playing."
...I just loving left the game out of the blue. At will. No second thoughts, either.