It sounds to me like someone has entirely too much time on his paws! You don't mention if you have done any obedience work with this dog (i.e., classes)? Does he have a crate? Perhaps a little time in the crate when he cannot be supervised more would help curb this problem. I would recommend your wife taking him to obedience class to establish herself as higher in the "pack" than he is. Does he do this more when you're not home, more when you're home, or does it seem to make any difference?

You could try bitter apple on the pillows, although I wouldn't put it on the bed pillows as you don't know if you'll have a problem with sleeping on the stuff. It is not supposed to stain or discolor, but try it on a hidden part first and see how it does. It is really quite nasty tasting and may help break this cycle.

You also don't mention how you and your wife respond when he does this. Do you yell and chase him (what fun -- a game)? Do you give him something in exchange for the pillows (I did a good thing, because I'm being rewarded)? Or do you just give him a "drop it" command and expect him to obey? Then, you could calmly put the pillows back where they belong and find him something better to do. Sometimes, strong negative responses become positive reinforcement, because they garner attention he is not ordinarily getting. Try not to make a big scene about it. Calmly take hold of his collar and the pillow and tell him to "give" or "drop it". When he complies, praise him profusely for being a really good boy. You might also work on teaching him "leave it", where, when he heads for a pillow place, he gets told to "leave it" and when he does, he gets praise rewards and loving. If he doesn't "leave it", he gets it taken away (calmly) and then is praised for giving it back. Take him with you when you return the pillow to place and give him a stern "leave it". Then, walk away and encourage him to come too. If he does, praise, praise, praise.

If the whole process becomes too much of a hassle, perhaps some "time out" in his crate will allow tempers to cool and let you get back into a more tranquil state of mind. I would close bedroom doors and keep an eye on the couch pillows all day. I know it's a chore, but the alternative is a naked couch and a very frustrated dog and wife. He needs some activity for the energy he has and obedience training will help. He may be six, but he sounds like the type that will be a puppy until arthritis slows him down and makes him mature.

The other possibility I see here is to perhaps work with him on his leash in the house. That way, your wife could keep him close at all times and have more control over what he is doing at any given moment. If he goes for pillows while on lead, she can give a quick correction to get his attention off the pillow and give him something else to do -- a bone, a nylabone, a tug toy, anything else.

I hope all this helps and hope, too, that you'll keep us posted on how he's doing. And welcome to the site.