Masada commented:

I would theorize that individuals who can spend great life effort on planning for the next 100 or 1000 years already have a pretty good handle on their immediate needs. They can afford the luxury of 100 year planning. Which by itself is an interesting point...

What if certain members of a society could be selected at birth to be 100 year thinkers? All immediate material needs of these individuals would be covered by the State. While I am certain you can find a number of practical flaws, it is an interesting concept. Perhaps you can create 100 year thinkers by ensuring they don't need to worry about things in this lifetime.