If you feel you need one, take one !
I trust yoiur motivation and willingness to succeed, so if you feel exhausted you should listen to yourself :
- you will come back to case prep. with even more motivation
- you brain will have digested the work on case study and should be able to work faster when you return
In any case, exceeding 100+ case in a prep. doesn't seem the best idea. You will never be able to cover all the case possibilities you will face on d-day, so I always recommand to focus preparation on quality and not on quantity of cases. How to focus on quality : adjust continously your practicing to the dimensions where you need to improve. This require a good diagnostic and use of specific exercices such a structuring drills instead of running through tons of case studies.
Enjoy your hollidays !