After you have made the first yogurt, you can use part of it to create the next one. Theoretically, you can keep doing this as long as you can keep the yogurt cool.
Yes- I sometimes take a small container and freeze some so there's a reserve yoghurt culture, literally 'on ice', in case the main batch loses health. Frozen, the yoghurt culture can remain viable for several months...maybe longer.
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Good idea, thanks for the hint. Will try.
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