You know, Brita should hire me as a "brita barometer".
Simply by drinking water, I can tell when it's time to change the filter. After 20 years of drinking only filtered water, my Crohn's will start acting up when the Brita filter has stopped working and I'm basically drinking straight tap water. Generally, the filter says it should be changed every 2 months. Well, not in this house. We use the water so much, that it needs to be changed at least once a month. No need to mark it on the calendar or adjust the dial showing which month it needs to be changed.....just ask me and my Crohn's.
It knows....it always knows.