Correct tire pressure benefits you in many ways. The Number one reason is safety, improper inflation can cause instability and may even cause a blowout!
Other benefits are improved gas mileage, better and more even tire wear, and a more comfortable ride. Tires that are in good shape with a proper mount shouldn’t need to be checked very often. Start by checking the pressure every month or so. If there is very little fluctuation each time, start to lengthen the interval. Always check before a long trip. Things that can effect tire pressure are air temperature, tire temperature, and of course leaks. It is best to check your tires under the same conditions each time.