Hi,
Patting yuna's head has nothing to do with the night ending too early.
The nights length is by default 1:30 min and can be extended by upgrading the SD card in "Cam" pane accessed from the MC's computer screen. Besides that the night may end faster if:
- you're caught either by Yuna or Kan (glasses guy)
- you run out of time
- you press the "end" button next to the time
- you have low stamina/battery life
What you experience is probably due to the low stamina you have after the day runs, which at night becomes a camera battery.
Cheers