Chocolate Lab runs away

Question
My dogs name is Charlie. He is Choc lab 3 years old. well trained but he keeps running away. How do I train the dog to stay at home(when I am home)with out physical restraints (i.e. locking door or electric/wireless fence? The problem is Charlie is trained to stay home and knows he shouldn't go but when he gets bored and opportunity presents itself (I fall asleep or get busy) he takes off to find friendly dogs in neighborhood. Do any training methods exist in order to stop this behavior. This behavior slowly started 6 months to a year ago but is increasing more and more. When I am home, I have never locked him up and 95% of the time he stays home. I have yelled and spanked and also tried positive reinforcement when he does stay home with praise and treats.

Answer
Is a physical fence out of the question? The thing is, if you don't see him go off the property, you can't correct the behavior. The more he gets the chance to reward himself by visiting other dogs, the less "trained" he becomes. If you use positive reinforcement when he's home, that doesn't really address the leaving and the yelling and spanking is most likely to make him more reluctant to come to you or be caught when he has gone walkabout. He's proven that you can't trust his "training" to keep him home, so I'd be supervising him carefully and not giving him the opportunity to roam. I'd also be giving him plenty of exercise and training to keep the boredom to a minimum. Sandy Case, MEd CPDT www.positivelycanine.com