A few of the saddles I'm not currently riding have developed mold, as I keep the bikes in a barn in a humid climate (upstate NY). I kept the saddles in the freezer for a few weeks, hoping to kill the mold. I took them out this weekend, and they're inside at room temperature. I will see if it helped. If it didn't, someone told me not to worry about the mold, as he claims it doesn't harm the leather. In any case, I didn't worry about the temperature of the freezer harming the leather.