@pleco_breeder
You don't lose the account, your books or credits earned.
Your account gets downgraded to free user status which locks out the members only forum sections, including the discussions about the current pre-pub books.
It also hides the "Purchase Credits" button in the 'My Account' part of the site, due to this being a Membership perk.
'My Library' should still be accessable, since those are books that you have paid for. At least it has always been for me if I took a break from membership.
When you go into the 'Titles' page and click on a completed volume, aka one for sale, the gold button on the bottom of the list changes from 'Premium' (letting you buy with credits) to 'Go Premium' taking you to join.
If you have 3 Credits available for your account and wanted to use those credits without taking your account to Member or Premium level again, someone would either need to give you a direct link to the purchase page, where you could spend your credit, or you could send an email to support, where someone would help you make your purchase.
Hope thats helpful.