Evidence - both historical and from contemporary sleep studies - seems to indicate that most people tend not to sleep longer than about eight or nine hours a night, regardless of how long is available. What happens instead is that you have two periods of sleep, broken by an hour or two of being awake. This was used for all sorts of things, from visiting friends to good ol' fashioned humpin'. This did indeed start to die out around the Industrial Revolution, however: not because people had more free time (seriously, try a farming lifestyle without modern innovations and tools - or just watch any of the Farm series that the BBC did - and see how much free time you have), but because of the advent of electrical lighting and an increase in places like all-night coffee houses.