The title of the fourth book in Douglas Adams's The Hitchhiker's Guide to the Galaxy, "So long, and thanks for all the fish" is the message the intellectually-superior-to-humans dolphins leave as they depart Earth just before the Vogons show up to demolish it to make way for a hyperspace bypass. Don't worry - the dolphins save the day by constructing a duplicate Earth and transporting everything from the original Earth onto it before the Vogons destroy the original Earth, thus saving the human race.
So what does this have to do with associations?
What happens to your members when they retire from the industry your association serves?
Do you offer them nothing more than active professional benefits at an active professional price? Do you kick them out because they no longer meet the standards of membership?
Or do you provide ways for them to move to an emerita/us status and stay engaged in different ways that make sense to people who've stepped back from active day to day involvement in the profession?
What might that look like? Has your association been trying to launch a mentoring program? Most mentoring programs suffer from too many prospective padawans and not enough Jedi masters (to mix my sci-fi metaphors for a moment). Retired members and young members are a match made in heaven (or at least on Tatooine) for cross-mentoring. Are you short volunteers who can help with the doing, not just the planning and issuing of orders? Your emerita/us members have time and expertise. Do you need people who can help orient new members? Trust me, your staff doesn't know what members need to know, but other members do. Are you trying to run a fundraising campaign and need people to make initial contacts? Your retired members can give, use their Rolodexes to help you identify prospects, and use their career's worth of contacts to open doors.
Don't leave your retirees with no option but to say, "So long, and thanks for all the fish!" Find ways to engage their expertise in and passion for your industry or profession in ways that make sense for them.