You’ll remember more of what you study if you break up your study sessions into shorter blocks of 20 to 30 minutes each. Your brain remembers more of what you study near the beginning and near the end of a study session so take advantage of this by scheduling shorter study sessions.
Also, you’ll be better off studying for an hour a night for a week than studying for seven hours the night before the ASVAB test. There’s only so much information your brain can absorb at one time so those seven hours spread out over seven days will do you much more good than those seven hours jammed into one evening.
Your most important asset going into the ASVAB test is having the confidence that you can do well and that confidence doesn’t come from cramming the night before. If you just commit to an hour or so a night for a week or two you’ll almost guarantee that you’ll score high enough to earn the job you want.