We have a carbon filter water purifying system at home. The company
which sells us the filters recommend a filter change every 12 months.

There are only 3 people in the house and we only use the water for
drinking water which is about 1.5 - 2 Litres a day.

I know from experience that the carbon filter is *used* when you can
taste the tap water.

Everytime we change our filter, we never reached this point where we
can taste the tap water - would it be safe to continue using the
carbon filter until we can taste the tap water?