Retailers are boasting Nintendo's Wii U Pro Controller will last up to 80 hours "on a single charge". As reported by Nintendo Life, both Gamestop and Amazon feature product descriptions that reveal the supposed battery life. Although Nintendo hasn't confirmed this, I assume the descriptions were provided by the platform holder.
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.
While some may be disappointed in its lack of backwards compatibility, the longer battery life is more than enough to make up for it. In comparison, most PS3 and Xbox 360 controllers offer 25-30 hours of charge. The WIi U touchscreen GamePad offers just five hours.
Unfortunately, the Pro Controller is not included in either of the Wii U console bundles. It can be purchased separately for $49.99 from retailers.