I once ran into a book that, no joke, was a scholarly work arguing that the Roman Empire fell due to hitting peak wood and should be taken as a cautionary tale for us in the field of fossil fuels.
I, too, remember the post-Roman centuries of the "Great Eurasian Desert", during which no trees existed, and mankind existed only as a few straggling bands of nomads.
On topic, though: no way the "nine years" claim about Saudi oil are accurate, but their own claims aren't accurate, either. Or, to put it more accurately: there's probably enough oil for all of that, but
getting it out would be prohibitively expensive, to the point that even using wind-mills (
without subsidies) would ultimately become more cost-efficient.
That's the reality of "peak [x]". Not that we'll literally run out, but that as you use up the easily-available reserves, only the (increasingly) harder-to-exploit ones remain. This inflates cost (exponentially, over time), which means alternatives -- even ones that are currently more expensive -- will ultimately be cheaper in comparison.
(Anyway, this also proves that "peak wood" is a ridiculous bullshit claim. There were trees all over the place. Although it may be argued that "peak wood"
was reached in certain regions at certain time in Antiquity. Notably Phoenicia, where they used so many trees for ship-building that they significantly increased desertification in the region, which meant that the remaining trees were more valuable if kept in the ground -- where they could help prevent agriculture-ruining erosion. Which naturally harmed their ship-building capacity, and ultimately contributed to their decline. Resources do matter. But "we will literally RUN OUT!" has almost never been true, in history.)