I mail like a fiend, religiously, monthly, Promos Jan-Apr., Quarterly newsletters, educational/lighthearted correspondence all the other months, follow-up survey, and yes, reminders @ 6;9;12;18;24;36 mo.
Too much? I thought so; so I surveyed some long term, and big spenders, 8 out of 10 said they didn't mind in fact they like them, esp the newsletters, they look forward to them. Two said newsletters were enough, so that's all they get now, the rest said , "what's the big deal if they don't want them, don't read them, toss em out."
Let's face it you can't force people to clean, but you can be the first one they think of when they happen to decide it's time, I was surprised at how many clients will say in their survey responses,that the mailer got them to, or reminded them to call.