You start multiple cultures so that you can have them at different points in their development. You can get multiple generations out of a culture given that there is enough medium, not too many dead flies, etc. Somebody said seven weeks from one, I still have production from one from late February (mela). That said, you also need some flies to start new cultures and there are different takes on which cultures to start new ones from (freshly hatched etc). At any rate, part of it goes back to the better to have and not need axiom. I start cultures every two weeks and have more flies than I need. I would keep a good amount of cultures and then scale back. Also, get your vivarium seeded with springtails well in advance of your frogs. I have a booming population in the vivarium, and even with the frogs doing there best to decimate them see good production in the LECA. I don't know about false bottoms, but my springtails breed like crazy in the LECA. So far I don't need to supplement from my springtail cultures, but have them going just in case.