How long should you study for a post test

You should study for as long as you feel necessary. Study until you know the material and have confidence you will pass the test.

Depends on the person, subject, course load, and the amount of time you have. Personally for all of my tests, exams, etc. I always use the 30.5 rule. 30 minutes studying, 5 minutes break, repeat. I do that for about 4-5 hours on Mondays, Tuesdays, Wednesdays, and Thursdays. Fridays are my relaxing day - 10 minute flash card review, 5 minute break, repeat for an hour, then read a summary of your notes.