No study is needed when you are the dean. 3 shelf exams are hard, but it is not excessive. In undergrad we could not defer final exams if we only had 3, and yes each were on average 2-2.5 hr long. Step III is 2 days long, so get used to grueling testing.

There is plenty of time to prepare for cummulative shelf exams if you review all semester long.

If you are one of the people having a hard time balancing your time between masters, and med. you need to get your priorites straightened out. Medical school should be #1. If you can not handle the load then drop masters.

We should be glad the shelf is only worth 20%. If you can not pass the subject shelf you should not pass the course, no exceptions! If we want good board scores, and to be taken seriously in the US we need to go the extra mile. This is just an IMG fact of life.