That $55 for 6 months was a fantastic deal. I signed up with that too. You couldn't be a member to take advantage of it. It's not a bad idea to let it lapse and see if there's another deal. I think that's a good stance to take with all subscription services. You won't want EVERY month. If you tend to buy a few SS releases, it will save you money. The member pricing on colored records is a few buck cheaper than the retail price and they will ship them with your SS subscription. The real membership perk is most black vinyl for $9.99. You sometimes have to wait a month or two, but it gives you time. If you haven't listened to it in 2 months, you probably don't really want it.
I've swapped probably a third of the ROTMs for either previous ROTMs or just regular items in the store.
If you want to know when you're getting your ROTM, you have to use USPS Informed Delivery, but none of the subscription services are great with that.