If the benefits of a new idea will start to come through in six years’ time, and the full benefits in 20 years, is that idea likely to be implemented?
It is, in fact, worse than this. Before the benefits become visible there will be a negative period of confusion, the disruption of systems, criticism, criticism of cost, etc. All the negatives may be visible or imagined immediately – but the benefits can only be seen in the future. And only if you are minded to see them.
Would a politician with a four-year, or less, time in office before the next election risk all the negativity while enjoying none of the benefits? It is not very likely.