FFXI is the first game I have ever played where I got over 30 days of gameplay time, and don't even feel like I have scratched the surface of what I want to accomplish. There are soooo many goals, so many things you can do, so many quests, and many things you can do that are fun just to pass the time... After all this time, this game still feels like it is new to me. Not to mention even over the short time period I have played they added in many quests and features, and they are making an expansion soon
I think the $13 per month I pay is a steal... So in FFXI's case, I'm all for a monthly charge. Certain games shouldn't have charges though, but the MMO world should.