At what age do they stop being little shitbags?

As above! Barty is 2 now and every time I think he's maturing he takes a step back! Today I went out to the supermarket for one hour. He was shut in the crate and when I got back he had destroyed the dog bed. Stuffing all pulled out. Shredded. My other dog was with him but he's older and I know it wasn't him.

He gets an hour's off lead run every day. He's never left alone for more than a few hours because I work nights. He has constant affection, treats and new toys. He's basically a spoilt brat.

It stresses me out so much when he destroys something because I dont know if I'm ever going to be able to trust him to be left unsupervised. I want to be able to leave him in the house when I go out and not be rushing to get back in case he wrecks something.

When do they stop with the separation anxiety? Do they ever? Do they ever calm down?