There have been games over the last 12 years that have held my interest for a year or more at a time. Most of those I've revisited for extended periods as well. It is possible. It also had nothing to do with pay model.
The days of buggy and lag ridden 2 or 3 hour raids being acceptable have been over for a long time. TOR is proving that even as we type. I hope that they change more than just the billing style.
Yeh, for me there have been games like that as well, TOR being one of them. Thing is, for an MMO to keep interest is a personal thing. I doubt over 90% of the MMO's you played and grabbed your interest for such a period of time, got me bored after a month or two at best.
Beyond that, yes there are some issues on the latest raids, however they are minimal and in general do not prevent progression. As far as lag is concerned, I have none.