Ha - another sufferer from the beeping car syndrome! My Fairmont doesn't even have a cancel function for that. After a while, the low fuel sign will come on too, but nothing will stop the thing beeping. Oh well - at least I'm never likely to run out of petrol. Yes, I try to keep at 1/2 tank or above, too.
It also beeps at me if I turn the motor off and the headlights are still on, but that's a good reminder and easily solved. I don't mind that one.