If you lose all normal AC and DC generators, flying on emergency power, does an ADC/IRS get power for up to 30 minutes? I believe that is the case on the 757. When the 737's batteries are dead (and you had better be in VMC or you are....) will the IVSI get useful info from an air pressure source which requires no electric power? That might be a good question for a check airman.
Does your flightbag have a handy flashlight (torch) with good batteries?