I agree -- you definitely cannot go by one or two years of performance to judge.
Take the 73 + 74 period:
Bill Ruane (Sequoia) was down 44%
Charlie Munger was down 73%
Rick Guerin (Pacific Partners) was down 90%
Yet, these individuals all had successful long term track records --- better than most you can find. Walter Schloss was only down about 15% in that period -- did it make him any better? No -- but he was in an elite group that included the other 3 .... and a select few others including WEB, Peter Cundill, etc.
I can't say much about Sprott as I also do not follow him either. But I can say that in 2008 Tim McElvaine was down about 50% and in 2007 he barely broke even. The market got very out of whack in it's pricing of things in 2008 --- Prem did very well in timing the fall. But if you think the market had wrong valuations on the way up --- it is more than likely it had a lot wrong on the way down too. Judging an individuals record as being superior for a short time such as a huge fall is just as wrong as judging an individuals short term record after a huge bubble.
UCP / DD