How long is to long?

Hi hfbamafan, I like the fact that you're already looking forward to preparing yourself for the GMAT. The question of whether 4.5 months is too long, too short or just right for you (the classic Goldylocks dilemna) is one that only you can answer.

Instead of quoting you statistics and past experiences, let me turn the question around. If you started studying today and felt that you were ready in 2 months, would anything stop you from taking the exam in June and getting it over with? In other words, if your score needs to be settled by October, why would you wait until September 30th to take the exam? Just start prepping whenever you can and take the exam when you're ready. This solves all your timing concerns, gives you time to adjust if it ends up longer than you expect, and guarantees you won't "burn yourself out" or get bored or anything.

If there's a given timeframe you need to adhere to, then by all means stick to it. Otherwise, start whenever you're motivated and take the exam whenever you're ready.

Best of luck!
-Ron