[Typical Length of Reading List for Art History Qualifying Exams?]

Hi everybody! This is my first time posting to this forum so I hope I'm doing this correctly. I am about to begin studying for my PhD Qualifying Exams in Art History, and I am trying to get a sense of the average number of books Art History students read for exams in other graduate programs. The professors in my department have ZERO consistency amongst each other when assigning book lists. Lists range anywhere from 50 to 300 books, with 4 month reading period. When the graduate students tried to address this discrepancy in a meeting with our Director of Graduate Studies, we were told "This is how it's always been done," and "Exams are supposed to drive you crazy." The general lack of respect for mental health in my department is an issue for another day. 

Unfortunately, my advisor is on the higher end of the spectrum, and my current major list is about 250 books long. I am majoring in Italian baroque art, and she has asked me to read literature spanning between 1400-1800, in addition to literature on France and Spain. She doesn't expect me to read every book in detail, and instead wants me to understand how each book has contributed to the field. This is what she was asked to do as a student at Columbia in the 90s, and insists that this is the best way to proceed. 

Naturally, I am a bit overwhelmed about all of this, and I could really use some perspective on how other art history departments structure exams. Any advice on how to study this much material in 4 months would also be greatly appreciated. Thank you!