Question

What is a natural resource that cannot be replaced except over thousands of years or more?

Answer 1

Oil

Explanation:

That are no natural processes presently operating that would create new sources of oil or petroleum. The theory is that large number animals were buried in a catastrophe that ended the Mezazooic Era.
The buried animals were changed into petroleum as heat and pressure converted the organic material into petroleum.

The chemical reactions changing organic material into petroleum can happen very quickly. Germany during world war II being short of petroleum resources created "artificial" petroleum using heat in a chemical process.

The process of changing organic material into petroleum can take thousands if not millions of years.