An architect, a fine arts painter and an engineer were discussing  whether it was better to spend time with one’s wife or his mistress.

The architect said, “I enjoy time with my wife. This helps build  a solid foundation for an enduring relationship.”

The fine arts painter said, “I enjoy time with my mistress,  because of the passion and the mystery I find there.”

The engineer said, “I like both.”  “Both?”   “Yeah. If you have a wife and a mistress, each will assume you are spending time with the other and you can go to the lab and get  some work done.”