He's getting out of the corporate world. A few years of double duty can be worth it.
It's not a way to live forever, but for people who can work like that, for a few years it can suit them really well.
The con of the startup racket is that so many people think they're buying their freedom with the 16+ hour days (and have been misled into believing that) when, in fact, the proportion who actually become billionaires or major venture capitalists is pretty terrible.