I will never use a conventional grout again after having found SpectraLOCK two part epoxy grout. It is comparable to conventional grout for installation but it never needs to be sealed and it will never stain. I have used it on a ceramic tile floor and a marble tile floor. It wears like iron... probably will never need to re-grout! It is available locally at Lowes. You buy the clear epoxy and hardener separate from the colored filler (sand). The filler is available in a variety of colors. The SpectraLOCK also has a mildew-icide so mildew will never form on the surface and the epoxy is impervious to all micro-life. It is a lot stronger than conventional grout and is more flexible... able to overcome minor movements.
JUST SAY NO to conventional grout! I will NEVER use conventional grout again!
http://www.lowes.com/pd_328840-73069...7C1&facetInfo=