The subject kept popping up in the comments, and mbp has a nice blog entry about it: An surprising number of people feel that getting a lifetime subscription is a good deal, even if you don't plan to be playing LotRO non-stop for the next 18 months. It is not a purely economical decision.
A monthly subscription is like a ball and chain, tieing you to a game and restricting your freedom. Getting rid of that restriction is worth something to me. I could buy 6 months of LotRO for a bit over 50 Euro, of a lifetime subscription for 150, so normally the break even point should be 18 months. And I'm far from sure that I'll play LotRO for the next 18 months, because of other interesting games like Warhammer Online, and the next WoW expansion coming out in that period. But I am going to pay for the lifetime subscription anyway, because it gives me greater flexibility.
I like World of Warcraft. I am pretty certain that I will buy the next WoW expansion. But I'm so not willing to hang out in WoW after basically having "finished" the fun part of the Burning Crusade expansion. I'm also looking forward to playing Warhammer Online, but I'm not going to sit here twiddling my thumbs waiting for it. All of this means that the way in which I play MMORPGs might change. Instead of sticking to one game for a while, and then giving it up, I might switch back and forth between two or three games. Just like you'd want to watch the latest episode of a TV series when its on, you might like to play the latest WoW episode (be it a content patch or an expansion) when it comes out. But between these WoW episodes you might want to see the episodes of LotRO. A schedule of playing LotRO now after release, doing a bit of WoW after content patch 2.1, then coming back to LotRO for the June content patch and so on sounds feasible, although I'm not yet sure how it will work out in praxis.
And a lifetime subscription for LotRO helps here. Because right now I'm looking at my WoW subscription and ask myself whether I want to cancel it, and for how long. Maybe I get bored of LotRO in a month, and then I wouldn't want to cancel my WoW subscription. Maybe I'll be playing nothing but LotRO for the next six months, and then I really shouldn't waste a hundred bucks on WoW during that time. By taking a lifetime subscription to LotRO, at least I won't have the same problem in the other direction. I can stop playing LotRO without worrying about a monthly fee.
Tell you what, Blizzard: You offer a lifetime subscription for WoW for $200 / €150, and I'll buy it. For the reasons stated above. Which I think is a generous offer from me, seeing that WoW right now is acquiring a whiff of "past its prime" scent.
Dear readers, how much would you be willing to pay for a lifetime subscription to World of Warcraft right now?