I just read about Thomas Sullivan, who between family and his job as a high school teacher, only had two minutes to write each day, in the school library, before the bell rang for his first class. He managed to squeeze out a paragraph, day after day. Driving to school, he would be writing in his head, and by the time he sat down the words were in order and ready to be recorded. He managed to write three books this way, including a horror novel called Born Burning, as well as dozens of short stories. Finally he was able to quit his job and write full-time.
I write in tiny chunks sometimes, but no shorter than five. Maybe I need to set my sights lower.