The 3 minute, 30 minute, and 3 hour study approach. What you can possible learn (or review) in the time available. It's layering applied to studying. It works well for work. Decide how much time you will give to a task and do the best you can, while making sure you complete the task within the time limit.
3 minutes: For a whole course might mean just reviewing the subject areas.
30 minutes: 3 minutes for overview, then 27 minutes for more detail. You should do a complete cover of the material at greater detail. However you can elect to spend more time in areas that need the effort.
3 hours: Do a 3 minute survey. Do second pass with a little more detail, it doesn't have to be 30 minutes. Maybe only 10 minutes. Decide on a plan for allocating your time. Several areas of very higer detail or everything to a high level of detail.
There are several benefits of this. One you develop a sense of how long it take to complete things. You're not likely to hit your time limits and goals when you start using this. So forgive yourself and recognize that you are learning a very valuable skill, that few have, so stay with it.
Another benefit is that you will avoid a pit fall of overstudying in one area to the detriment of others. People are tempted to study in the areas that interest them the most and in the areas that they find the most difficult. Interest is a great motivator, but it is also a very strong distractor. To stay focussed and achieve your goals, be aware of how you are spending your time and decide what time you will dedicate to each goal. In regards to the difficult areas, often the information YOU need is contained somewhere else, and you spend more effort that was necessary learning something. Sometimes, the incubation time is all that is needed. However, sometimes total emersion is indeed necessary. You should consider which tactic to use. I'll say that the wide to narrow, is probably the best on average, and in the worst cast of total emersion it doesn't waste too much time before you get to the emersion strategy.
Getting back to your Exam studying problem. You don't have to do the 3:00 - 30:00 - 3:00:00 everytime you study. But develop a strategy and get into it. Also if you get to that point where you think you know everything, and it does happen for some students on some courses, then you turn the envelop around. There's no value in review something you don't understand 3 minutes before you go into an exam. In fact, search the forum for exam tips there is some good advice on getting yourself in the best mental and physical state to perform.
Thanks for the post, it good to make me think. It's amazing what you leave on the roadside of life without noticing.
Good luck,
Iam2 
