A bit late here, but-
I'd like to echo the previous posts, and add some thoughts of my own:
It does take a bit to get the things going. My first couple of weeks I sat on the culture like a mother hen and in retrospect it probably was contaminated, or at least slow to get going. After that, the thing really took off though, and there was no question about it.
Once you have the culture really established, it will take quite a bit of abuse, like being left alone for a week on the counter, and still recover quite nicely. Once or twice I thought I had killed the little buggers and I spent another few anxious days watching and waiting. I simply fed the culture daily whether it needed it or not and in a few days I had it roaring right along again.
I now keep two cultures going: one in the fridge which gets fed every two weeks, need it or not, and my working stock (just lives on the counter) which gets used at least twice a week. I also like to take a sample of it when it's really at full kraeusen, pour a thin layer onto foil, dry it then grind it up in a food processor. Then I have a dry culture which can be shared (or stored for if I ever really do kill it).
I have had this bunch going for over four years and I don't see why it shouldn't last forever. It is really wonderful stuff: Pizza, bread, tempura, fixes trucks, cures colic, works on stains.........did I mention it makes great pizza the world's best pizza?
