Stress cracks?

I was just wondering if anyone has had stress cracks while using an UTH (Zoomed in particular) and a moist substrate. The heat mat warns that if there is water near the area the heat mat is under, it could cause a crack in the bottom of the terrarium. The Eco Earth I prepared is still a bit moist, and I was concerned that if I setup the tank, the moisture could cause a stress crack. Anyone have experience with this? Is this even something I need to be concerned about? Any advice is appreciated, thanks.

I have only seen it when people use the mats without a thermostat.
ALL UTH should be regulated.

Ok, cool. I have a thermostat, so my mat will definitely be regulated. It probably not get much hotter than 90 degrees