Maybe that what he is pointing to?This is like asking how long one can build a house without specifics about the type of house, size, and location of it.
For creating a new mine, it totally depends on the type of ore, expected yield, location, the geologic and geographical conditions. For example, it could take years to just build 100km of roads to a lithium reserve 5000 meters above the sea level. It would certainly take much longer to build facilities appropriate for mining uranium than iron. The list can go on and on.