That's a fantastic question. I have heard that you can freeze sourdough starter for quite a while, and it will maintain its ability to do its thing after some coddling. I have some frozen right now as a back-up to my fridge jar, but haven't tried it yet. I'm thinking that maybe the good bacteria (well, all the bacteria) goes dormant, and then starts to revive as it thaws. I freeze milk and cheese and all that seems to change is the texture.

Let me know if you learn more.

Anyone else have ideas?