Cramming info in your brain only works if you are planning on taking the exam within 24-48 hours. All you are doing is memorizing all the info in your short term memory and short term memory is easily accessible for retrieval. But only 20% of that info will be retained after the 48 hours time frame is over. For some students, cramming before work to their advantage, but you do not truly learned the material, you just learn to memorize.