I haven't been keeping corns long, but others who live in warm places have posted that they turn off their heat mats for the summer. I have done the same and things are well.
Keep an eye out for nighttime temp. drops if you do, though. I had just turned my mats off because it had been very hot in the house, then I fed a large meal, and that night the temps. dropped quite low. I had one regurge as a result. No problems afterward, and at this point there's no chance of low nighttime temps. where I live, but it's something to be aware of.