Earlier quoted context omitted.
Assuming lithium reserves work anything like oil reserves, the quantity of reserves depends on market process. When oil sells for $20/bb, oil that costs more than that to extract doesn't count towards the reserves. As the price goes up, the reserves increase, because you can extract oil from more challenging circumstances. This is why we've had 20-30 years of oil reserves for the last 50 years.
Oil alarmism existed as early as 1919: http://papers.sae.org/190011/
I mean, sure, if we search long and hard enough we will probably almost always be able to find/produce something, but I don't think asking 1 million per liter of gas would be such a great idea.
Hoping that there will always be a scientific breakthrough just "right in time" to solve our resource problems is great. I love optimism. It's also extremely irresponsible to depend on it.