I just realized that a really nice move for a stacker assuming you just want "ounces" (or pounds if you are so lucky and inclined).
Take your higher-premium items and trade them for lower premium items now.
NOTE: This works even if you prefer the higher premium items.
Here's the math:
Eagles are currently spot + $2.99.
Generic is currently spot + $1.
Spot at the time of writing this is $18.86.
When spot was $35 those numbers were roughly unchanged.
Let's say you have 100 Silver Eagles and that when trading you have to pay a "trade cost" of 10 cents per item you trade. (That should be lower assuming you can trade larger quanties and/or do so in person).
So you trade your 100 eagles for 109.46 generic rounds. (I'm going to use decimals to make the example more clear. It works as there would simply be a proportional cash payment to offset this in a real trade.)
Math: (18.86 + 2.99) * 100 = 2,185.
2,185 / (18.86 + 1.00 + 0.10) = 109.46 (I rounded down to ensure I didn't enhance my own argument)
Later, hopefully not dozens of years later spot is now $35.
So you trade your 109.46 generic for Silver Eagles and you now have 103.45 Silver Eagles!
Math: (35 + 1.00) * 109.46 = 3,940.56
3,940.56 / (35 + 2.99 + 0.10) = 103.45
Therefore: Right now the goal should be to obtain as much of the lowest premium possible. Then when silver is higher trade that for the higher premium stuff.
Buy low premium when silver is down.
Buy high premium when silver is up.