I have unlimited hearts and I don't pay for subscription. I don't know if there is a glitch with my account or maybe my streak is so long (>1500 days) they have just given up on trying to monetise me.
I'm the same, I just figured I'd been grandfathered into something. Although I don't use the app any more since they redesigned all the courses last year or so; it's worthless now.
Be careful, there's guaranteed to be employees reading along here :)