The purpose of these adjustments is to ensure vehicle-travel that is smooth when driving along a straight and level road and to maximise tyre life. Incorrect alignment is a major cause of early tyre wear. Over the years, a properly aligned vehicle can add thousands of miles to the tyre life.
Follow the vehicle manufacturer’s recommendation noted in your owner’s manual. But, usually you should have your vehicle’s tyres checked every 10,000 miles or at least once a year.