You can set never archive younger than at policy level. EV by default will archive 1000 items in a mailbox and then move on. Should the user have more than 1000 eligible items EV will send them to the ack of the A5 queue to make sure it gets back to them.
Once all eligible items are taken EV will not retry mailboxes it will simply idle.
This statement is true of scheduled runs. with a "Run now" you can tell EV to archive every eligible item or any number you fancy, and that uses the A3 queue. To stop it archiving once it has begun you would need to purge the A3 queue.
A5 is different and will only proccess during the scheduled archive window, which is why if it is constantly ful, you are not allowing enough time for EV to archive.
As for finding the policy settings that would be in the admin guide.