Q & A:

Is porcelain tile more durable than ceramic tile?
Yes, in most cases, porcelain is a harder material and is solid. Ceramic tile in most cases is a clay backing with a ceramic glazing on top.
Should I use bleach to clean my grout?
No. Bleach or any other harmful chemicals can break down the color pigments in the grout, discoloring it badly. A mild tile and grout cleaner is best.
My tile is cracking in the grout line and through some of tiles. What does this and how can we stop it in the future?
More than likely you have a small crack in the concrete substrate and its transposing through the tile and grout. Remove the offending tile and grout, apply a rubberized crack isolation membrane, retile and grout.
How often should I reseal my travertine?
About once every year or two depending on how much use or traffic the stone experiences.