Sourdough is a super stable super difficult culture to kill once it is established. Mine lives in the fridge, in a 1/2 pint mason jar, and it is fed every week or two. If I scooped out the entire 30-40 grams leaving a residue on it, I could add a bit of water, wipe the sides with my finger to get the residue to cloud the water, feed it some flour and have a thriving culture by the end of the day.
When I want to bake, I can take 18-20 grams of it, feed it some water and flour in the morning, and that evening, I take the recently fed starter and add enough flour and water to make my levain, which is ready the following morning to be mixed with the dough.
The window is flexible enough so that I could use my levain 12 hours later or 24 hours later (if refrigerated) and get a great bread.
Been making pizza with yeast lately and have really enjoyed it. But I will be trying sourdough in the near future (I had some great success using the Tartine country loaf dough for pizza but want to branch out to get a good idea of what I like working with and eating best.