Originally Posted by
shadowline
... it answers half my question (what happens to my points), but the other half (how can I keep my points without having an MR-earning card) is still un-answered,
It answers both questions. The points vanish if you do not have a card which participates in Membership Rewards. You need to transfer before closing the card account. Unless you have a very large points balance it doesn't seem worthwhile to pay for a Green card simply to keep them.