I'm curious how many hours one needs to wear a watch in normal daily acitivity to keep a 40 hour reserve movement fully wound. It probably varies with activity level, but let's say you spend 8 hours at the office, take a walk for lunch, do something active with the kids after work, eat dinner, get a good night's sleep. At what point in your day could you switch watches so as to keep a second watch wound? Perhaps different movements are too variable to come up with a rule of thumb, but I'd be interested to see if there is a consensus.
P.S. I do know all about watch winders, folks! This is a thought problem - - not a real problem in search of a solution.