An architect, an artist and an engineer were discussing whether it was better to spend time with the wife or a mistress.
The architect said, "I enjoyed time with my wife, building a solid foundation for an enduring relationship.
The artist said, "I enjoyed time with my mistress, because of the passion and mystery I found there."
The engineer said, "I like both."
"Both?" they questioned.
The Engineer said, "Yeah. If you have a wife and a mistress, they will each assume you are spending time with the other woman, and you can go to the lab and get some work done."