When to remove shadecloth for the winter?

[Ray]

OK, so this summer I had to cut down a 100-foot tall tree (had been struck by lightning and died) that used to be my "shade cloth", so replaced it with some 35% Aluminet (great stuff, by the way).

As this is my first time using shade cloth in 40 years of growing, when would be a good time to remove it - remember I'm near Philadelphia, 40°N latitude.