Scalping a lawn to buy an extra week between visits removes the leaf area the grass uses to feed itself, and exposes soil to direct sun. Two weeks later you have thin turf and a weed problem.
Three inches, and never more than a third
St Augustine wants three to four inches in summer. Never remove more than a third of the blade in one cut, even if that means mowing twice in a week after rain.
Sharpen the blade
A dull blade tears rather than cuts, and torn tips go brown. We sharpen ours weekly, which is why a Verde lawn looks cut rather than chewed.