Generally speaking, sealing a concrete driveway every 2 to 3 years is normal. But there are several factors which can vary that approximation.
Is it a spray application, or a squeegee application? How many coats are being applied?
Is it a quality product?
How detailed was the preparation or cleaning of the concrete done prior to applying the sealer on the last application?
How much traffic is there on your driveway?
How much exposure to the sun does the driveway have?
Do you live in a snow region where the department of transportation uses Magnesium Chloride or de-icing salts?
Do you use de-icing salts or any other de-icing chemicals yourself?
These are some of the factors which can determine the life of a good concrete sealing job. Be careful, however, not to seal the driveway too frequently as that can cause more damage than good.
Watch our series, "The Most Common Ways Concrete Repair Contractors Rip Us Off and How To Avoid Them"™ before hiring any concrete repair contractor.