Are you applying in R1 or R2? If you are applying in R1 obviously November is too late for visits to impact your school choices and essays. If you are applying in R2 it's the perfect time to visit. A school might come off your list or become a higher priority after visiting. As long as you're visiting before you have to make a matriculation decision any time is fine. Visiting prior to applying is more for your benefit than the adcoms (except for maybe Tuck and Johnson where it's important to the adcom too).
The Brain Dump - From Low GPA to Top MBA (Updated September 1, 2013) - A Few of My Favorite Things--> http://cheetarah1980.blogspot.com