Charlie's the same way as Duncan. If I take him out but it's too cold for me to stay out with him, he won't play by himself. We normally play together about 2 hours a day, plus our 1 hour walk. He doesn't want to play alone. But he definitely whines, barks, and makes funny growly noises in the house when we're not on our normal routine. All that energy to burn!
Pat makes about the best justification I've heard for having more than one dog. If Charlie had a playmate, he probably would exercise without me when the weather's bad. Until I raise "this one" though, I'm miles away from adding a dog.
Can I "rent-a-dog" on cold days? ...just kidding...