You want to keep their mailings coming WITH the paid reply envelopes. The post office needs the business!
“Hint: Be careful to remove all evidence of your name, address and any code numbers which the AARP might use to identify you.”
Great advice. Have you gotten yet any of their post-paid envelopes with a transparent window where the AARP address would normally be? They include an insert with their address on one side, and *your* name and address on the other, so they can start identifying those folks who mail back their crap.
(I xerox the AARP side (reverse side thus blank of course), and then use that to send the envelope back, basking in satisfaction that they had to use more expensive envelopes to get boomeranged yet again).