It kind of depends what the work is and if it's tiring. Take someone like Warren Buffett - he's reading and thinking pretty much all working hours but it's what he likes to do and not especially tiring. Seems to work quite well in that case. The only real downside seems to have been his family complaining they didn't see enough of him.
That is not to say that there are others who can do many actual productive hours. But usually, at least in my personal experience, when one does that they are sacrificing other aspects of their personal life in the hopes that when they achieve their goals they can then deal with everything else.
In my experience, things don't really work out all that well. Ideally one should find balance in the now.