We've already been warned of one major issue with smartwatch usage - Not only do the manufacturers all seemingly list a nightly-charge routine, but it seems likely that these devices will barely last a full working day idling without requiring a charging cable to be used.
Obviously this isn't optimal, with users often charging their smartphones daily alongside other portable devices including tablets. Apple have been reportedly aiming for a 19-hour window, alongside 2.5 to 4 hours when in constant use. This is a stark contrast to ASUS, who are apparently going to use a simplified chipset and mobile operating system to ensure extended use.
ASUS chairman Jonney Shih has proudly stated "the ZenWatch is defined by us as a companion of a smartphone, and we think it still has a lot of room for improvement," further commenting that "as a companion device, its central processing unit and operating system should be more simplified than the current version, so that I can use it for up to seven days on one charge, rather than for just two days."