I've been doing tile for twelve years now and have never damp cured ever. The polymers that should be in your grout (latex) slow down the curing process to make your grout harder. I did see one couple who actually did do a damp cure and I admit they're grout was incredibly hard; but this isn't as necessary as you might think nowadays. After you grout, you can walk on your tile, just walk in the center of the tile, like your walking on stepping stones crossing a river. After a couple hours you probably won't hurt it. I wouldn't do any work on top of it untill the next day. Keep your animals away from it; their claws can dig in to the grout before it hardens. I still have marks from my cats dragging their claws through it trying to figure out what the grout was. Grouting tip of the day: Don't use a lot of water while washing. The water shrinks the grout and makes your joints lower. Put your sponge in the water and squeeze really good so it's pretty much just damp. Also make sure while your floating that you get the majority of grout off the surface if you can; this makes cleanup a lot easier and makes your grout go further.