On that post about a bird that fly for 6 months in a row there were a discussion about the sleep in animals. Some of them are able to sleep alternating one half sleeping and the other aware of the environment. And there is speculation if that bird could sleep while flying.
I think half brain awake is not enough to have a fully functional life. I also heard about people losing part of their brain and adapting to deal with it. But that doesn't mean a brain doesn't need that part. It is like the fallacy of using only 10% of the brain. The brain is very well used and optmized for performance, if you lose part of it, it would adapt to compensate what is missing, but it will not be optimized anymore.
Disclosure: just guessing here, I have no scientific knowledge or background at all to support these claims of mine.
In the case of the bird, it may not need fully optimized brain to fly. So it might be acceptable to have reduced brain performance as a tradeoff for longer awakeness, especially if you could recharge under reduced performance and then go back to fully awake (and rested).
I think half brain awake is not enough to have a fully functional life. I also heard about people losing part of their brain and adapting to deal with it. But that doesn't mean a brain doesn't need that part. It is like the fallacy of using only 10% of the brain. The brain is very well used and optmized for performance, if you lose part of it, it would adapt to compensate what is missing, but it will not be optimized anymore.
Disclosure: just guessing here, I have no scientific knowledge or background at all to support these claims of mine.