Yeah, I'd base my hoarding strategy strictly on mintage figures. There were more 1964 nickels minted than all the other years prior combined. (Almost 2.8 billion 1964 nickels were minted!!)
I don't think any amount of years will make a coin more valuable, until you start talking hundreds and hundreds of years. It's more about scarcity, i.e. how many were minted. Just study the mintage figures. For Jefferson nickels in the 1960s, I'd keep 1960-1962 in P mint mark only, and 1968. That's because those varieties were under 100 million mintage each. Even those will take a long time to be valuable, and probably only in real nice condition.
Those buffalo nickels aren't valuable just because they are old and the design is different, it's because they weren't minted in the huge quantities that the next designs were minted in. Buffalo nickels had an average overall mintage of about 18.5 million per year. Some years much less, some years much more.. but that's the rough average. Compare that to Jeffersons at an average overall mintage of 327 million per year. So Jefferson Nickels overall, on average, were minted 18x as much as buffalo nickels ever were, per year. That is why buffalo nickels are generally worth a whole lot more than Jeffersons. (Plus it was a bad design that resulted in dates wearing off, making ones with readable dates even more scarce). If they would have minted over a billion of any date buffalo nickel, I doubt that date would ever in your lifetime be worth more than 5 cents. It doesn't matter how cool or different the design is.... there would be enough of them that they just wouldn't have much numismatic value. It's about scarcity combined with condition. You have a good idea of the condition, but if I were you I'd re-evaluate scarcity of dates if you are going to hoard them with the idea of them gaining value.
Do some CRH and look at all the dates you find. I just finished a box of nickels, and there are plenty of all sets of years out there. I got a handful in the 30s and 40s, plenty in the 50s, and bunches and bunches in the 60s. There were lots of newer nickels, but old dates even into the 40s and 30s are not uncommon at all. They just made too many of them.
I'm not trying to be argumentative, just trying to help shine some light on it. I talked to the guy at my coin shop today and he agrees 100%.
Most of my Jefferson nickel collection was handed down from my grandfather to my father to me. The whole thing isn't worth much at all, and it probably won't be when my kids hand them down to their kids. There are a few dates that are worth a little, but it's because they were LOW MINTAGE.