I'm no longer a member, but I had some store credit left and was tempted to try to use it before the ship is completely submerged. I signed up for a month yesterday during swaps, placed an order through the store to use up my credit, and then canceled my membership so that I wouldn't be charged. It seems to have worked; I wasn't charged immediately for the membership, and when I log in, I'm asked to join the club.
Oh, and the best part, I got a shipping notice for the Sun Ra LP I ordered this morning. That's the fasted shipping I've had in months!
All that is to say, if you're a former member who's sitting on store credit but didn't really want to pay the exorbitant shipping charge or the higher nonmember prices, you might consider trying that approach--rejoin, use up credit on a store order, and cancel immediately afterward.