Washington State Extension was advising that the later the pear, the longer the pre-chill requirement, and there were advising to pre-chill the late-season Anjou pears for something like a couple months at subfreezing – 30 degrees?
That recommendation apparently went down the Memory Hole at the Ministry of Truth when they said, “Hey, growers are getting good results with pre-chill at warmers temperatures for a shorter time.”
It used to be that I threw out my Anjou pears because I could never figure out how to ripen those billiard balls. Last year, I brought in my Anjou pears from Northeast Wisconsin, Door County and put them in the cool garage. They were ripening so fast after 2 weeks in there that I could hardly keep up eating them, and they were sweet and juicy as an Anjou should.
No rules! Try different things and record what works.