I agree with what you say about trying to make sure of having an insurance policy that has no age cut off date. I certainly wouldn't want my insurance to be cut off as I am reaching the age at which I am more and more likely to need it.
As for what will be required for O retirement visa holders, maybe requirements will change and maybe they won't. Many have convinced themselves that they will. However, the fact remains that so far I have seen no indication whatsoever that will happen. Even if it does happen, we don't know whether requirements will be grandfathered in.
I learned a very long time ago to follow the advice of one of my old friends, a prosecution attorney in Florida: "Don't worry until you have something to worry about." That is good advice and so far from immigration there is nothing to worry about. I'll do my worrying if and when some sort of official change comes out if they start requiring something I can't comply with. I won't be losing any sleep over rumor mill predictions.