MMORPGs don't keep my attention long; I haven't played a single one over a 6 month period; most I get sick of after 1-2 months, that's usually when I hit the level cap and realize that the end game sucks and there's nothing else to do besides move onto the next grind....... I mean game.

As for other online games; D2 was in fact the longest and kept me playing steady for five years then off and on after that; Pangya I've been playing since Season One and DnF off and on over the years. D3 and DFO will be my next addiction; guaranteed I'll play for over a year.