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 he enjoyed time
with his wife, building a solid foundation for an enduring
relationship. The artist said he enjoyed time with his
mistress, because of the passion and mystery he found
there. The engineer said, "I like both."

The other two went, "Both?"

And 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."