Absolutely not, but mine are not on it all day either, so perhaps someone else here who utilizes theirs for longer periods of time could better answer that.
They are not a hard rubber, but very similar (only thicker) to the rubber tires for vehicles are made out of. They are flexible, but heavy as heck to move. They are great to walk on, easy to clear of snow, ice, dog "stuff", easy to sterilize if needed, soft for the dogs to be on (a lot better than concrete, although they do lose the benefit of wearing down the nails naturally, so you have to watch those and keep them clipped).
Overall, the only downside is the heat during the summer, but like I said, if you paint them, (or simply keep the dogs off of them when they are hot) they work great. Mine are painted with a non-toxic paint on one side beige, and left the other side black (summer/winter). I think the dogs who stay inside all day on the carpet have worse wear on their elbows than the ones outside do.
Hope that sheds some light. :)