I wonder whether there's a degree of intelligence beyond which one no longer values existence -- a point where drives no longer have effect.
That's a good one!
It gave me pause to think. I think it may depend on what you mean by drives, and on how you define existence?
There's a Buddhist saying that goes something like this (as best as I can remember):
In the first stage of enlightenment there are mountains.
In the second stage of enlightenment there are no mountains.
In the final stage of enlightenment the mountains return.
What I believe this means is in the beginning we are filled with questions about existence. And anguish over the meaning of it all.
When we reach the second stage we realize that existence doesn't really exist. (The Buddhist maintain "There is emptiness at the heart of all matter"so therefore existence is an illusion.)
In the final stage we now understand all that there is to understand. We have no more questions, so we can sit back and enjoy the illusion for what it is.
We can live life just for the sake of living it.
The Zen Master goes to the well to drink its cold water. He knows the well and its water are an illusion, but that does not stop him from enjoying his drink. In fact, his enlightenment makes his drink of water all the more pleasing.