Do they eat furniture if left in the home for three or four hours at a time?
It can happen. As with any creature dogs can get bored. If bored, they will try to eliminate the boredom. One way to prevent this is “crate training”. Using a veri-kennel or other brand “crate” you can insure the protection of your Dane as well as your other property. Most dogs see a crate as a surrogate den. Just as in the wild, a house dog likes a place that is just theirs. A crate is a great den.