I'm interested in your opinions about day trips. We get a lot of questions here, and some just seem ridiculous. "We'd like to see Mont Saint Michel, the D-Day beaches and cemeteries, maybe take in Belgium, and back to Paris for our dinner reservations." I wonder why someone would want to spend hours getting to Edinburgh and then go back to their more expensive London hotel room.
I think my personal limit would be two hours there, two hours back, but less travel time would be better. Anything more is just too exhausting, and would be better as an overnight. Your guidelines?