The sealer tells you before the concrete does. 

Look for these signs:

• The color has gone flat. Stamped concrete that used to look rich reads dull and washed out.
• A white or chalky haze. The old sealer is breaking down and losing its clarity.
• Water soaks in instead of beading. Splash some water on the surface. If it darkens the concrete instead of sitting on top, the protection is gone.
• The surface looks gray and tired even after you hose it off.

Any one of these means the sealer has failed and the concrete underneath is taking Colorado weather with no protection. T

he concrete itself is almost always fine. Catch it at this stage and resealing is all you need.