Picking pre-1960 is arbitrary (I technically also save some of the lower mintage 1960+ nickels).
But I think there are a few reasons that 1960 is the cutoff date that was picked:
1) Around 1960 is when the mintage of nickels started to increase substantially.
2) The first whitman folder for Jefferson nickels covers 1938 - 1961 (theoretically the cutoff date should be pre-1962 if this was the true reason #1)
3) 1960 is roughly the date in which pennies were switched from wheats to memorials and roughly when the US went off of the silver standard for coins
Looking at a recent price guide, the prices of 1964 and older jumped a bit over the last year or two, but the newer stuff did not. Personally, I can't see why 1964 jumped as you get at least one in almost every handful of nickels.
With regards to selling pre-1960 nickels. I have heard of a few people having luck selling them either on eBay or at local coin clubs and such, but I don't believe they bring much of a premium, at least not yet. I think I heard they typically were going for around $3 a roll. I heard this all secondhand so I don't know if I have my facts straight or not. In my opinion the harder to find dates are a little underpriced still so I have been gathering them up while I still can, but only at face value

.
Part of the reason they are underpriced though is that there are still too many circulating.
Section10 said:
Thanks for the responses. One more question:
Being not far from Canada I see a few Canadian coins as well--especially pennies. When did Canada last make copper pennies as I assume they are using zinc now also?
Thanks
Jim
I can't remember the exact date(s), check
http://www.coinflation.com and look under the Countries menu for Canada. Based upon metal content value, you can figure out the date transitions.