I spent 4 years on and off studying for the GMAT. I would study for a month get distracted by something else and then take a two month break. Start studying again for another month, get distracted again, and then take another break. All in all I probably spent a good 12 months studying for the GMAT. Of course most of the time I spent studying was re-learning/re-reading many of the subjects that I forgot.

The last time I took the GMAT I spent a good 5 straight months cramming for the GMAT (cramming = 20+ hrs/week). I would suggest that 3-4 months is probably sufficient for most individuals, of course, your study time could vary depending on your desired score (higher score = more study time).

Learning at a slower pace may actually help you retain the material better than someone who whizzed through the book. My suggestion is to read through everything slowly the first time to get a firm grasp on everything and then whiz through the book a second time through.

I would highly recommend postponing an October test date if you do not think you will be ready in time. You can still apply to MBA programs next year if you take the test in January/February.

There's no such thing as a slow pace for studying once you set your mind to it. You must put a great deal of effort in to both the quant AND verbal sections - do not assume that you won't have any problem with the verbal. Alternate your study time with each of these sections so you won't feel overwhelmed and confused. Try to study in the time of day when you are least tired, if possible, and stick to a study schedule. Get organized and stay cool.If you don't feel you're ready by September or October then wait another month or two. The trial tests are a pretty good indication of where you stand and you do have another chance if you don't score well the first time. Best of luck!