Often, if they are respectful from the jump, are not calling from a big call center, speak clearly, and I'm not too busy, I'll tell them the actual situation, which is not now, but they can try me again in 6 months because my parents are aging (my stepdad, rapidly) and live in the next state over, and there's a possibility at any point that I may be moving back to help one or both out with care, or possibly take possession of their homes, should the worst occur. And they still travel, a lot, to like Europe and such. And they are motoring enthusiasts, and their vehicle of choice is an old, rather unsafe type of car. They don't live super-safely, in a nutshell.
So, all told it's not unthinkable that I'd suddenly need to end up elsewhere, with more property, possessions, and responsibility than I'd ever desire to have. Ergo, when the time comes, there's good chance I'd just want to unload this current home in pretty rapid order, so I tell them it's fine to try me from time to time. At this point a couple of them have done exactly that, checked in every 6 months.
Sometimes they're annoyingly persistent after I tell them all this, but not typically 
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