According to both Gamestop and Amazon, the Wii U Pro Controller is said to have a battery life of around 80 hours for a single charge. This is a drastic increase compared to the Wii U Gamepad controller, and for comparison, most PS3 controllers tend to last 20-25 hours.
While this number hasn't been publicly announced by Nintendo, both Amazon and Gamestop use the exact same product description, which makes it seem like these descriptions were provided officially by Nintendo.
Here's the rub:
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 the 80 hour play time is certainly a plus, it looks like the Pro Controller won't be compatible with Wii titles, meaning you should hold onto those Classic Controllers if you still have them.
For an in-depth look at the Wii U Pro Controller, check out our hands-on impressions.