I leave mine on, too. It has an auto shut-off and I never used to even unplug it...
Let me tell you, though, that we did almost have a fire. Not because of ME!!! When our (old) bug service came into my sewing room to spray, the guy moved my iron - onto the faceplate, did his spraying and left it - on the faceplate! It turned itself ON, steamed all the water out, burned the ironing board cover and burned itself up! When I came home and smelled it, I completely lost it! The ironing board was already rusted. It could've been a very serious problem.
Now, I unplug the iron when I'm finished for the day and we have a different bug service. They never spray in the sewing room.
Lesson learned. (My husband is an insurance broker so you know how loud he can talk to remind me to unplug it!)