You make some good points. However, the conditions in your area are not necessarily the conditions in other areas. People in other locations might find that they need to do something a little different.
To your points:
1) You will probably not know 2 weeks ahead of time if something traumatic will happen. If it does, you can reschedule so long as you do so more than 1 week ahead of time. So in other words, even if you register 3 months before your test date you still have until 1 week before the exam to decide that you will actually take it on that date. The rescheduling fee is only 1/5th of the cost of the exam itself.
2) It is true that the test is widely available, but not in all markets. In many cases the exam spots fill up more than 1 - 2 months in advance. Some people also have certain limitations, such as they must take it on a Saturday or they can only take the exam during the afternoon time slot, not the morning or evening.
It is important that each person who is thinking of taking the exam go to MBA.com and see what the availability is like in their area. If you can see that there are very few time slots that work for you then you might want to sign up sooner rather than later. Again, you can always postpone if you are not ready at that time.
3) It is true that there is no cost savings for registering early.
In short, there are some good reasons to consider signing up early. In particular if you wait too long to sign up you might:
A) have to take your exam at a time of day and date (or day of the week) that does not work well for you - simply because that was the only time left.
B) have to travel to another city and spend the night in a hotel because there are no time slots at the testing center nearest to you. This can end up costing more than the exam itself. And it can be difficult to get a good night's sleep in a strange location. Better to sign up early if the center nearest you is one that fills up quickly.
C) have to wait several additional weeks - even though you are ready to take the exam now. It may be that there simply are no time slots left and you cannot travel to a distant location to take the exam. In which case you may have to wait several weeks beyond when you would like to sit for the exam.
To sum it up: if you have an extremely flexible schedule and can take the exam on any day of the week at any time and if you live in an area with many test centers, or the test center nearest you is not a busy one, and if you are not sure when you want to take the exam, then you might consider waiting until you are ready and schedule the exam for 1 - 2 weeks later.
For everyone else, it is probably better to schedule your exam in advance so that you can take the exam at a time that works for you, on a date that works for you, at your preferred test center. Go to MBA.com right now to see what the availability situation is in your location.
Thanks for beginning this discussion. It is an important one for people to consider.