I tested all my aperture priority auto expose capable cameras (Canon, Minolta, Nikon, Olympus, Pentax & Ricoh) and found only the LX to be capable of hours long auto exposure. Also, unlike the others - with the exception of the OM's, it constantly monitors the scene for changes in lighting and will adjust accordingly + or -.

Regarding adjusting for reciprocity, I am certain most all film makers only account for up to minutes long.