Just kidding.
I would say it depends on the time of year. The month before in service, 1-3 hours a night, depending on how busy you are.
Usually, I'll read 30 min to an hour a night. This will consist of focused reading and preparation for procedures the next day. On the weekend, I may sit down once and read 2 hours or so from Campbell's or AUA eLearning.
Finding time to study during your residency requires discipline. Or meeting with your program director to explain a poor in-service score. You'll figure it out.