An architect, an artist and an engineer were discussing whether it was better to spend time with the wife or a girlfriend.

The architect said he enjoyed time with his wife, building a solid foundation for an enduring relationship.

The artist said he enjoyed time with his girlfriend, because of the passion and mystery he found there.

The engineer said, I like both.

Both? they asked.

Engineer: Yeah. If you have a wife and a girlfriend, they will each assume you are spending time with the other woman, and you can go to the lab and get some work done.