I don't crate mine when I leave. He's been trustworthy with free reign of the home since he was maybe 7 months or so. I'm careful to puppy-proof always, as in, I can't leave food out. No food on the counters, on desks, tables, etc. The trash is in a covered bin, and there's a tall baby gate blocking off a room with my cat's litter box. Oh and we have to lift all of the window blinds - he loves to destroy those. He doesn't have separation anxiety fortunately so no howling.
The worst things he's ever done when I've left before I wised up was get into the "cat candy" and leave a huge stinky mess, eat a bag of chips or something that he stole from my desk, or got into the trash and left a mess. I used the crate to potty train, and he was solid in about 6 months while I lived in an apartment. Now I just feed him in there. Since it's his space, when he goes in on his own no one can bother him.