A method and device for indicating whether a dispensable product will require refilling prior to the next scheduled service interval includes tracking the amount of use over a first interval, and calculating a frequency based from the use over the first interval. The quantity remaining is compared with the required amount, which is the product of the number of weeks in the service interval and the calculated frequency. Thus, when the quantity remaining is less that the required amount, a warning will be provided to indicate that the dispensing product should be replaced, as it will be empty before the next service interval.