"After a raid has exhausted their attempts for the week, the Ashen Verdict must withdraw their support and the four most difficult bosses all despawn and become unavailable for the week. The limited attempt system is a feature of both Normal and Heroic difficulty."
See this is the bullshit that makes wotlk raiding annoying. Not only that there is only 1 instance that every one does at a time since all the previous instances drop so bad loot its next to impossible to motivate people to go there (whens the last time you did sartharion or maly?).
But to top it off you have a "number" of atempts now that you can do before you can't play anymore.
I mean in TBC if I wanted I could raid 7 days a week 4 hrs a day. It was my choice. And some of the older instances still had items that even a black temple raider needed (dragon spine trophy , items from vashj or khael)
Now its next to impossible to raid for more then 2-3 days a week. I hope they fix this in cataclysm. Even tho i've quit in wotlk since it's painfully obvious that its not a proper game but a beta test, I would like to purchase the expansion in case they finally decide what they want from the game