This comes from a GameStop listing for the Wii U.

Your games, your way. However you think of your gaming style – hardcore, old school, or purely nostalgic – the Wii U Pro Controller puts you in the game. Designed for accessibility and extended gameplay comfort, the Wii U Pro Controller features the dual analog sticks and ergonomic button layout that you’ve come to expect, as well as a rechargeable battery that can last up to 80 hours on a single charge. The Wii U Pro Controller can be used for playing a variety of games – from packaged games at retail to downloadable games from the Nintendo eShop. Look on the back of Wii U game packaging to see which games use the Wii U Pro Controller. Not compatible with the Wii system or games.

If true, this is a pretty hefty amount of time for the Pro Controller to last. Of course, this is probably the max time, with perfect conditions.  

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