when I mix it, it stays mixed, the oil doesn't separate again, granted it only lasts 1-2 weeks on my shelfs.
It such a chore to mix it up, I go into a state of horror at the thought of having to mix a new jar whenever I finish a jar. I always leave an unmixed ring at the bottom too. Specially when I buy the bigger jar at Costco, it's hard to get the spoon all the way down.