How many photos can a digital camera take?

In the early summer of 1826 Joseph Nicéphore Niépce of France made a permanent photographic image on a polished pewter plate coated with bitumen. The exposure of the view from his window took eight hours, so the sun appears to be lighting both sides of the picture. Niepce had been successful in making paper negatives in the camera obscura as early as April 1816, but was unable to fix them (render them insensitive to further action of light).