According to Precision Stoneworks, the resealing schedule for a granite surface depends on the color of the granite. Once a year is sufficient for dark, dense stones, while light-colored granite may require resealing as often as every three months.
There is no need to reseal the granite if water beads up and stays on the surface. Granite is moisture-resistant, but its surface is permeable, and many substances, such as cooking oil, vinegar and candle wax, quickly soak into the stone and stain it. Ammonia, cleaners containing acids and abrasive scouring powders etch the surface of the granite and reduce the effectiveness of the sealant.