When an adult dog misbehaves, how long before he forgets what he did?

MY two Border Collie/ Red Tick Hounds remember everything they do. I can come home and if they've gotten into the garbage or eaten the cat's food no matter how long its been they remember. When I punish my dogs I like to use a squirt bottle and I spray them right in the face. It sounds mean but its one of the things the vet told me to do. Sending him outside might be sending mixed messages like you said, he wont put going outside together with a punishment. Another thing we do at my house is crate them. I put them right infront of whatever they did wrong and I leave them there for a few minutes. Being an outside dog he might think that when hes in the house he doesnt have to listen. You just have to show him that your the boss and that when you dont want him doing something he shouldnt be doing it.