The Airservices website mentions 9000 SARTIME s expire annually without cancellation.
I wonder if they all really needed to submit a SARTIME, how many originated from a flight school and were returning the same day?
Perhaps an iPhone or Android app with notifications? Doesn't matter if there's no signal, it can still tell you when your time has run out and you can work out how to contact them and cancel your SAR.
There is already one on your phone it is called an alarm.