The crystal ball comment is not helpful. The same argument applies to all forecasting. For instance next years budget may be invalidated by a financial crisis,

The crystal ball comment is not helpful. The same argument applies to all forecasting. For instance next years budget may be invalidated by a financial crisis, a war, a new invention. What a forecast does is provide a helpful generalization for questions like, 'can we really use Lithium batteries at that scale'. 80 years of expected availability doesn't mean we can will run out in 80 years, it does mean that in our short to medium term planning the risk of running out of lithium is low. So in the context of the question, 'should we be using lithium, as it is scarce?', the forecast is perfectly reasonably applied.