Lalvin 71B for one gallon question

I would like to start making some experimental 1 gallon batches and then scale up to 5 gallons if I like the results. For those who make one gallon batches and use 71B, do you use the whole pack or do you use half? I was looking at curt stock's recipes and he uses 10g(2 packs) for 5 gallons. So I was assuming 2 grams per gallon would do the trick.

There is a real risk in using only part of a package and then wrapping up the opened package and storing it. The risk is that you will allow or even encourage bacterial infection. Given the price of 71B and given the fact that the lab states that a whole package is good for fermenting between 1 gallon and 5. Your call, of course, but I prefer to minimize any risks I take and that risk seems to be a little unnecessary.