For me, I would say the vast majority of my landscape shots are f8.
This leads me into another question which is: Why does your landscape lens really matter much?
As long as your lens doesn't suffer much distoration and can handle chromatic abberation, aren't the vast majority of the lenses going to be great/sharp at f8?
What else do the much more expensive lenses offer?
I originally planned to sell of my 5D3 kit 24-105, but have kept it as a walkaround AND landscape lens. It sort of surprised me in terms of how happy I was with it...