"Just One More Turn, and I'll have built my Library/Probe Foil/Pyramids/Trance Plasma Shock Troops!" "Just One More Turn, and I'll have researched Monarchy, allowing me to change my government!" "Just One More Turn, and I'll have moved that Colony Pod where I want my new base!" "Just One More Turn, and surely Chairman Mao will have to admit defeat!" "Just One More Turn, and... oh, is that the dawn?"
Civilization IV acknowledged this explicitly, with the Quit confirm dialog offering the option "No...just...one...more...turn!"
Galactic Civilisations 2 has a quit dialog reading something along the lines of "Just one more turn won't hurt... Are you sure you want to quit?" It works - I never want to quit after reading it... --Anonyman