I keep more than just pre 60's. There are some incredible premiums that can be realized on mid to high MS nickels from the 70's and 80's. Just look at past forum auctions/sales on 1970's nickels. Of course its rare that you find them in circulation but that is of course why there is a premium. I also accumulate high quality 1982 and 1983 nicks for the same reason you mention. Rolls of BU nickels from those years sell very well on the Bay.