I agree 100%. I was feeling really beat in the last 45-30 min as well. Your mind starts to get easily distracted, etc.
I think it's really important, when you do your GMATprep tests, to mimic the real thing as close as possible. When you take your breaks, use the bathroom, eat something quick and start the next section. You don't actually get a full 10 minutes, because you need to include your check-in again. My breaks were closer to 7 min.
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