Kotaku: If I’m playing a single player game, do I have to be online at least once per hour or something like that? Or can I go weeks and weeks?
Harrison: I believe it’s 24 hours.
Kotaku: I’d have to connect online once every day.
Harrison: Correct.
So the system is built to work even if your Internet connection goes down, but you still have to be connected at least once a day to use it, according to Harrison. We're not sure exactly what would happen if you don't connect once per day—and that timeframe could change—but this doesn't sound good for anyone who was hoping to use Xbox One without an Internet connection.
Update: Sounds like things are a mess over at Microsoft. Now they're telling Polygon that Harrison's comments illustrate a "potential scenario."
"While Phil [Harrison] discussed many potential scenarios around games on Xbox One, today we have only confirmed that we designed Xbox One to enable our customers to trade in and resell games at retail," a Microsoft rep said. "There have been reports of a specific time period — those were discussions of potential scenarios, but we have not confirmed any details today, nor will we be."