I always put my pads on a folded hand towel and keep it on low which keeps the soil at around 75 - 80 degrees .. I adjust the temperature by using wash cloths between the pad and the pot with the seeds in it - unless the cord is frayed or cracked there shouldn't be a problem .. as I said, my are at least 20 years old and still work fine.
Yes, mine are also quite old. I did the same thing as to using washcloths between the toweling. We must have been on the same wavelength...