On cult of mac I saw this: "If your battery gets too low, Apple Watch automatically switches into Power Reserve mode so you can continue to see the time for up to 72 hours." How long can the watch go on a full charge in power reserve mode? Anybody have any info on this? Based on the above quote I would say as much as a week. Being able to let the apple watch just be a watch for an extended period of time would be a nice feature to use occasionally...for the times you don't want to be bothered.