OK first, 'there' is an adverb, what your after is 'their' which is a possessive pronoun! LOL sorry just a pet peeve.
BUT! What's the difference between what they are doing and what your proposing? If what you say is true and the game would be down for a week to do it all at once (which I find hard to believe) then you still get all the content in a weeks time anyway.. Not everyone plays every day of the week anyway so its almost the same thing. Anyway, releasing small bits of content over time I'm afraid isn't going to be enough to keep the population's attention. If they can keep this amount of content release on a schedule this consistent, then I think the game will continue to go strong. If they just do everything peace-meal then it might not be enough of an impact. To be honest though I'm not familiar with big game patches for MMO's, but I think I'm going to find myself taking a week minimum to get around to all the new content regardless!