"Q: How often do slots become available?
A: When a player’s session ends, their slot will become available. You will also move up the queue if someone leaves the queue and does not regain their slot in time. If you log out while waiting in the queue and want to get your slot back, you’ll have a few minutes to regain your slot. In the case of maintenance or any other server outage, there will be an hour for you to take back your place in line."
Basically, after a 3 hour session you can hop right back into the Queue to get back in.
Source: https://tlopo.com/news/post/96/