It depends on your perspective and your willingness to work their system to disable all mailings - or you will keep your recycler in business forever.
AARP is a lobbying and marketing organization. There are very few 'senior discounts' you can't get on your own - no AARP card is needed. When there is a need for an AARP card it is because the entity is a major sponsor and won't give a discount without proof of membership (think United Health Care, Walgreens, etc.).
Their magazine has some good articles, their monthly bulletin doesn't. There are decent articles on their website, but you can access by registering (and they'll bug you to join). They don't make $ on membership fees, they make it by licensing their logo to major sponsors promising they have data that can direct mailings to seniors in specific geographic and demographic areas.
With all of that if you feel strongly about senior benefits and retaining them they are very strong lobbying organization helping to influence legislation at the state and national level, so your annual (or multi-year) membership helps that it adds to a member count they can quote, but their funding comes from licensing arrangements (see above).