It's been reported today that Shigeru Miyamoto often spends around 10 hours a day playing games, in work. According to a translation, Miyamoto says he is "continually playing the games and checking their content, and sharing my opinion with the development staff." It's stated that he typically has around seven games on the go at once, which sounds promising from a Nintendo gamer's perspective.
Our very own Editor James Newton is currently undergoing a similar routine to bring you our comprehensive review of The Legend of Zelda: Skyward Sword, so he is getting a taste of the lifestyle. We're sure that playing upcoming Nintendo games is a serious business for Miyamoto-san, recording his experiences to report to the relevant game Director, for example.
That said, being an industry-leading genius in game design does clearly have its perks.