How to interpret 休息不了多长时间吧？
您晚上休息不了多长时间吧 is between interrogative and rhetorical. It means 


  (I reckon that) you don't have much time for sleep at night, do you?


There is a strong suggestion for the answer, yet an answer is expected to complete the dialog.

Word by word translation is like 


  You are unable to rest for long time at night right?