I thought we were passed this. He is a big strong dog so when he chews stuff, it's destroyed in seconds.
Only change is that we have increased his walks and indoor enrichment activities (kongs etc) so I don't think it's boredom. Everytime we have been to the vets they have said his teeth are amazingly clean and healthy.
He has plenty of toys/chews/bones/roots etc to chew on but is going for my kids toys, books, my shoes etc