I have cement tile in my sunroom. It close to 100 years old. I don't think it has ever been sealed. When I moved in, I tore out carpet that was glued down for at least 15 years. No damage. The cement/grout/whatever doesn't look good, but the tiles are all fine. I had to get some new tiles made for an area where I tore out a fountain (yes, a fountain), and a local tile manufacturer (Brothers cement tile) was able to match the existing tile just about perfectly.