I was just thinking about this myself. Assuming sanitation is good, why couldn't you crash cool it in the fridge and keep it? How is that different from leaving your beer in your primary for 2-3 weeks and then pitching on it? How is it that different from what white labs? I'm sure there are differences in these comparisons and lots of reasons not to do it but in my opinion, a starter that is put in the fridge rather than pitched should be good for a few weeks.