I don't use those vials - I use starter packs. I take the yeast off the bottom of my secondary and put it in a very clean 2L plastic pop bottle. I add about 12 oz. of sterile, unhopped wort to that and squeeze the air out of the container and store it at just above freezing. I can let it sit like that for a month. Probably longer, but I haven't tried. I have heard that people use baby food jars and put them in the freezer with a little yeast in them.
I don't think you should worry about it as much. If you can pour out 1/2 your vial and save the other half - even if it's in another sterile container - and you keep it cold, it will be fine. good luck!