I was browsing a Scientific American on the weekend and the metal second most in short supply, right behind indium, was silver! At current rates, if I recall correctly, it said our global reserves will last us until 2019, only 19 years!
I have looked for a link online but can't find one, sorry. Probably on the web site for subscribers only. I'll keep looking though...
By the way, gold was next, behind indium and silver.
No mention of lithium or rare earths. (The latter are not so rare I believe, plus they have quite a small global market.)