Almanac and Whitebeard

Sorry for the second post, I'm new to Outlier and started just a few days ago...

The Almanac and Whitebeard projects keep appearing/disappearing in my marketplace and when I try to join them the Accept and Add to Queue button is greyed out. Does this mean that the project is full? Is there a specific time that the projects refresh/add new hours or users that I should wait for? They pay considerably more than Aether (and I believe Aether is out of hours anyways...). Is getting on other projects basically a lottery?