When we installed our tile flooring several years ago, the installer recommended this product for sealing the grout so that it didn't start looking dirty or stained. After application, the water or whatever beads up and doesn't absorb into the grout. It says on the bottle that it will last up to fifteen years (15) but it doesn't. It will need to be reapplied every few years or so. Still, even that is a big help as an alternative to re-grouting. My husband was taught by the installer how to regrout our kitchen table because it had become stained. What a mess!! And time-consuming. So, I would much rather take some extra time and re-seal the grout as opposed to regrouting anything ever again!! I highly recommend this product to seal grouting. I would say it lasts four or five years at the most. In its defense, it does say on the bottle that aggressive cleaning methods may affect the amount of time it lasts and I do steam clean my tile floors.