Natural Stone Sealer and Enhancer provides color enhancement and sealing to most porous surfaces. As with all sealers, it also deteriorates over time, mostly dependent on direct sunlight and abrasion (traffic). Treated stone that is on a vertical surface will last 2 plus years. Stone that is in full sun on a well used pathway around a pool can require reapplication annually. Depending on how much "pop" you want your flagstone to have, you can reapply as frequently as you see fit.