Leaving a clothes dryer on as long as you're there in the house and can keep an eye on it is okay.
You don't have to be right at the clothes dryer every minute it's on but as long as you don't go to sleep or leave the house with the clothes dryer on it will be okay.
A neighbor left her clothes dryer on while she went shopping and came back to the back of her house on fire where her laundry room was.
The dryer shorted out somehow and caused the fire so after that I would never leave a clothes dryer running while I was away from home or asleep.
It's not worth the risk.
I always run the dryer when I'm gonna be home and if I do need to leave the house I shut the dryer off and then start it back up when I get home.