Twenty-five years ago I had quarrey tiles installed in my kitchen and porcelin tiles installed in my foyer. The installer never said anything about sealing the grout, and I have not had any problems. Recently I had ceramic floor tiles installed in a bathroom. The installer used polyblended non-sanded grout. He did not mention a need to seal the grout; however, the salesman at the tile store told me I needed to use a small paint brush to apply grout sealant. Will this really increase the life of the grout, or is he just trying to sell me something I don't need?