I have had the luxury of being able to spend ALOT of times with my dogs/puppies when I had them.
Honestly, it depends on the dog as to when they can be trusted alone in the house out of the crate.
I've had quite a few dogs over the years, majority gsd's, (still have two aussies), and again honestly, none of them ever really did any chewing of furniture/stuff..
I can remember two incidents, my aussie chewed up ONE of a very expensive running shoe, my fault she got to them, one of my gsd's chewed up a pillow and a canvas bag, again my fault they had access. Jake stole a cake off the stove once
All my dogs have been crate trained, my male aussie at 12 still is in a crate when no one is home to supervise (he's a trouble maker)...I've had 4 gsd's at one time, 3 males, 1 female,and all were fine in the house uncrated when no one was home.
Now, the two girls, (aussie and gsd) are loose in the house when no one is home, and again, no problems.
I do exercise / walk/hike my dogs alot, maybe they are slugged out when I'm gone