Oh got it. For use as a starter, a week (7 days) is about the max. I try to not go more than 5 days. But that's at 3-4C storage. At 10 C storage, you'd get 4-5 days, and you have to refrigerate as soon as you hit the right pH of 4.6-4.7.
My yogurt lasts 6-10 weeks in the fridge and still taste good stored at 2C. So it depends on your methods and temperature.
Yes, freezing is the best approach if you want longer term storage.