Most stained concrete floors have a floor finish (i.e., synthetic wax) over top of the concrete sealer. A certain amount of abrasion and scratching from foot traffic, children playing, pets, stationary objects and carts or dollies, over time, is unavoidable and will eventually erode the existing floor finish. The floor finish needs to be restored periodically so that the concrete sealer - and stain - below is not affected. If the floor finish is re-coated periodically, the concrete sealer, itself, should never have to be re-coated. How often to re-coat with floor finish most depends on the building environment. In homes, once per year is a good rule of thumb, whereas with businesses, it should be more often: at least once every 4 to 6 months.
A commercial grade floor finish from a janitorial supply house (local or online) should always be used - not one from a hardware or grocery store. The finish is best applied sparingly, with a garden sprinkling can, and spread with a lambswool applicator, or loop end mop, in very thin, uniform coats. (Note: loop end mops used for applying finish are slightly different than those used for damp mopping: they are made of a finer fiber such as nylon filament yarn or microfiber.) A new coat of floor finish should not take long to apply and will dry in 30-45 minutes, if not applied too heavily. Also, if the stained concrete floor has a scored or saw-cut pattern, be careful not to fill those joints with floor finish. Floor finish goes down milky white and may collect too deep in the cuts to clear up as it dries.
Floor finishes are inexpensive - usually no more than $20 per gallon from a janitorial supply house. They come in matte, satin, or high gloss, and vary in optical clarity and depth, as well.
Also, "Hazing" is a common problem encountered with floor finishes. It's caused by: 1) excessive humidity during application; 2) applying additional coats before previous coats have fully dried; or 3) applying over a dirty or contaminated surface. "Powdering", or chalking, of a floor finish is caused by: 1) applying under cold conditions (below room temperature or near poorly insulated exterior walls or entrances); or 2) applying over an unsealed or excessively porous substrate. These problems can be resolved by stripping the floor finish, correcting the source of the problem, and then re-applying more finish.