Yeah, regarding your first point -- the replacement brushes are also an Oral-B product, so prompting for frequent replacement of the brushes would be a way to make more money.
In my Sonicare, the brush heads have an NFC chip in them that stores the “runtime”. After xx uses an icon starts blinking on the handle and the app will tell you that the brush head needs to be replaced. But at least you’re free to ignore that and continue using it.
For now... Just wait, some bright-eyed underling will undoubtedly see this comment and then pitch their boss: "Man, oh man! I know how we can increase revenue, let's DISABLE brush heads when they hit 90 days and FORCE the user to buy a new one!" You've just doomed us all. >.< hah!