Very close to John's method - cheese to you, John! I have zip-lock small and large bags. The large bags I divide and label by "type" - geo, yeasts, coryne's, micrococci, PC, blends, etc. The small bags I just pinch down to the level of the remaining culture, and roll it up tightly before sealing, does a reasonably good job of keeping air out. Then I vacuum the large bag, and return to the freezer. I think it works reasonably well.