A lot, probably. You could sell people on the idea that it should be a part of your yearly health screening.
"And if you really care about your health you should do them every 3 months to catch problems early!"
or some such.
An ECG if it was just part of the normal yearly panel of things that get looked at I don't think ppl will stop doing it just because it doesn't find something right away
I do not consider the average HN commenter to be average.