Chewing instinct also varies from breed to breed. Dogs that have been bred to carry things around (labs, for example), usually will have a longer chewing phase than others, and may never grow out of it, really. We had a pair of lab-mixes that would chew on anything hard (especially wood). It was worst up until they were about 2, and the one that lived longer was still chewing on occasion at age 16, when he got bored. If it's destructive, find some toys, like Kongs, to keep him occupied and keep his attention off the furniture, etc. (My mom and dad never felt like it was worth the expense to buy the nice toys, and they would devour a rawhide bone in about 1 day, so that got expensive too -- I think the Kongs or something similar are the way to go, personally). Crate-training him would keep him away from anything you don't want destroyed while unsupervised, and that would be a fine time to give him toys to chew on. Eventually, you should be able to convince him that it's preferable to chew on toys than furniture, etc. Good luck!

If it's nipping/biting during play, work on training that behavior away like the other posts have said.