Keeping an installation looking new is not as difficult as you may think. Stone is naturally porous so a stone impregnating sealer should keep your installation protected. Depending on the traffic in the area will depend on how often you need to reapply. Regular cleaning the entire system with a neutral PH non-acidic cleaner should do the job. There are more harsh cleaners available and must use carefully by following all instructions. Always do a test area in a non-visible place