DNR orders

Do you know the DNR/full code status on all your residents off the top of your heads? Seriously. Forget the bracelets or other ways that indicate a DNR. (except the doc's order) You may think he/she is, but aren't quite sure. Our supervisor says all nurses should know the code status of each pt. In an emergency? ................
I'll be quite honest that out of 60 residents there are maybe 10 I can say right off the top of my head that I 100% know are DNR. BUT, is the order expired? I'm supposed to know this off the top of my head because running to the chart/computer is a waste of time in an emergency. Say the order wasn't renewed, pt expires. Now he's a full code. Pt/family doesn't want a full code. So if a pt has a DNR order, why does it have to expire? He should either be a DNR or not unless, of course, the pt/family changes their mind.