[fire]

ironically the special blue bristles in the philips heads that turn white when the brush head needs to be replaced is exactly what you want, I think?

[gwbas1c]

That's not the same, because it's gradual, as opposed to a beep / notification.

When things change gradually, I tend to ignore the change.

To put it in a different context, I've had the fadeout brush heads for years, but I had to get in the habit of changing my brush head when I went in for a dental cleaning because otherwise, I'd just keep using it forever.