Question: How long does a self-winding watch stay wound?
Disambiguated questions and answers: question: How long does a Rolex Oyster Perpetual from 1930 self-winding watch stay wound?
How long does a Harwood "bumper" self-winding watch from 1923 stay wound?
How long does a Miyota 8215 self-winding watch stay wound?
How long does a Chinese standard movement self-winding watch stay wound?
answer: 35 hours
12 hours
over 40 hours
minimum 40-hour
Natural Questions answer: roughly two days (from the Wikipedia article "Automatic watch")