We often jump to judgment with hens or roosters. Hens instinctively know how long that they can stay off the nest. In fact hens instinctively know more about sitting on eggs than I will ever learn. I think that is one reason hens who steal their nest away from prying human eyes, or meddling human hands seem to hatch a greater percent of their eggs than hens who "enjoy" our help. I don't know how accurate this is but some old-timers told me that hens act like your hen did to allow the eggs time to take up more oxygen. Until a better explanation presents itself that explanation works for me.