We at Raysco Inc. recommend thoroughly sealing your grout after any new tile work is done, but even those who have sealed it (or have had it done professionally) back when their floor, shower surround, or backsplash is newly completed should break out the sealer regularly (anywhere from every six months to a year) to keep that nice protective coating on your grout.
Some of the major reasons to seal:
Moisture working into the grout
Mildew and mold growing within the grout
Mildew and mold growing under the tile
You don’t absolutely have to, but it really cuts down on maintenance and keeps it looking mint for years to come. What does sealed grout have over non sealed grout? Well, by not allowing moisture or dirt to penetrate the grout, it relegates these things to the surface, thereby protecting the look of your lines. In other words: white grout stays nice and clean and white. And any other colored grout looks as good as new (all while warding off mildew and other gross stains). You will want to repeat the sealing every six months to a year depending upon your traffic, etc, just to head off nasty discolored or mildewed grout before it gets a chance to rear its ugly head. It’s just a smidge of maintenance to keep your tiled areas looking bright and clean, so we definitely think it’s worth the effort.