How much time do you need to play a game before you can review it?

The Ed Zitron Eurogamer review has become a running gag in the MMO web sphere. But nobody really answered the question of how long exactly you are supposed to play a game before writing a review.

For comparison, when I put up my Luminary review, I had played the game for over 40 hours, and reached level 38 with my main, plus had two level 20 alts to try out other weapons and skills. After that time I certainly understood how the game fundamentals work, what the game is about, but only for the lower to mid-level of the game. Somebody who would review World of Warcraft after playing it for 40 hours would certainly know how the leveling game functioned, and maybe have done a 5-man instance. But he couldn't possibly know anything about raiding or other end game activities. So his review would necessarily be incomplete.

But imagine the other extreme. Imagine I had not up to now written anything about Warhammer Online, but been busy playing it for 1,000 hours, and just killed Emperor Karl Franz, and done all the parts of a successful Altdorf siege. So I'd write my first WAR review now. Who the hell would be reading that? Sure, I might have a far more complete view of how the whole game works from start to end game. But the interest in a review of last year's games would be close to zero.

There is no question that in 2 hours (he claims 9) Ed Zitron couldn't possibly get more than a fleeting impression. But that is actually *more* time than many people would take to judge a Free2Play game, where the barrier to entry is just the time to download. Of course if you paid $50 for a game you probably play a bit longer before deciding you don't like it and giving up on a game. But I doubt anyone takes 40+ hours to make that decision for himself.

So, how long do you think a reviewer should play a MMO before writing a review? And how long do you play a game before forming an opinion about it?