It used to be six and a half until higher farm yields and productivity gains from automation produced enough surplus to even allow for less. From the dawn of urban civilization until well into the industrial revolution there was barely enough food to keep the population alive. Even if the bosses had been nicer about it that wouldn't have kept people from starving.
Yes I am aware that early hunter gatherers worked fewer hours per week and generally had better diets. But that lifestyle wasn't sustainable after the human population expanded.
At least in Judaism, all forms of labour, including domestic labour, has been strictly banned on Saturday, for centuries at least. They managed to survive alright.
More to the point, a recent series of history blog posts discussed this question, and it seems like for most of the population, the food supply was not really limited by labour but rather by food storage ability and land area productivity (which is different). For much of the year aside from during the harvest, there was a lot of leisure time (even if people were starving, that wasn't something that harder work would necessarily solve).
Yes I am aware that early hunter gatherers worked fewer hours per week and generally had better diets. But that lifestyle wasn't sustainable after the human population expanded.