Considering the game has been around for 12+ years, I'd say the game had a good run for a while. Obviously it won't hold interest forever. Heck, even WoW can't do that and that stuff is subscription based too so they have a constant stream of money coming in. I just came back to maplestory for nostalgia's sake and for the Re:Zero event (disappointing as it is) since I'm watching the anime currently and liking it thus far.
