May I suggest completely unplugging your irons when not in use? The reason: I had an iron a couple of years ago that was turned off, but was still plugged in. I hadn't used it in a few days.
The next time I picked it up, I was horrified that it was VERY WARM!
Apparently the switch/dial had malfunctioned. Thankfully it wasn't so hot that it could've burned anything, and thankfully I'd set it in a place where it wasn't touching anything else. The dial was definitely turned all the way off. DH was in the same room when I noticed it, and he looked at the dial, too. Yep, definitely OFF. Very scary. It could have easily been much, much worse.
Anything can malfunction. Unplug 'em to be sure!