Well here I go starting trouble -
If you're going to have a timer function, it might as well allow multiple entries. Don't want one? Don't enter one. Want a "Switch Tanks" message? Set it to fire every x minutes. Maybe have another timer to reset the DG and check the engine instruments every 15 minutes. If you're a flying diabetic, set a timer to test your blood sugar or eat the required snack every x minutes. If you want to get fancy, allow a "countdown" timer, too. For instance, to review plates/freqs/ATIS 20 minutes before arrival, or the required blood sugar check within 30 minutes of landing. Maybe allow for 0-10 unique timers.