Yea I have this toothbrush too, I also noticed the weird IC on the bottom of the brush head when I first bought it, I nearly correctly surmised what it did, was

Yea I have this toothbrush too, I also noticed the weird IC on the bottom of the brush head when I first bought it, I nearly correctly surmised what it did, was a little upset at the prospect of being forced to buy a new head when Phillips decided it was time, but it turns out it doesn’t really do anything, it buzzes a few times at the end of brushing when it thinks it’s time. And the LED changes color… who cares… The recommendation generally is to replace your tooth brush semi-annually, which this basically reminds you to do.