[boudin]

I found that saving a starter really depends on what you start with. In our case we were using store bought yogurt (the yeo valley brand) and after saving the starter 2 to 3 times, it wasn't much active anymore. One day we bought a yogurt from a local farm and have been able to save a starter and re-use it for months, we are still using it. We make yogurt every week.

[serkandurusoy]

I live in Turkey where yogurt is an essential part of our diet and culture and nothing beats a homemade pot with a thick layer of cream on top.

I can assure you, you'll never need to buy any more starter, ever! As long as you save some for the next batch, you're golden! If you can use unprocessed milk purchased directly from a dairy farm, that's even better as I promise your tastebuds will rejoice! :)

[bergie]

Same experience with starting from store bought yoghurt, only got 2-3 rounds from it.

[EL_Loco]

Do you know why that is? Is it the quality of the culture on the store bought? This also happens with me, however, the 2 rounds that I get from it are very good, thick, creamy yogurt, so I assume it has to have live cultures. Maybe I'm wrong?

[vram22]

You have to make each round using yogurt from the previous round, not the preceding ones (1), else the bacteria in the culture probably get too few / weaker due to less than optimal conditions, like temp., hours out, etc. (1) That is, batch 2 using starter from 1, 3 from 2, etc.

E.g. google videos of how to make kefir and see what they say about how to preserve and replicate the kefir "grains".

Exact same technique may not apply to yogurt culture, but principles do.