How do they know?

How do lovers know if they have found a good mutual-orgasm technique? There are several ways to tell:

• First, does it deliver a satisfying climax to both partners during a lovemaking session?
• Second, is it acceptable and comfortable for both partners?
• Third, does it still work on a Friday night when both partners are pretty weary? (Let's face it: most couples with children have limited options for private lovemaking time, most of which are times when they're not fresh and well-rested.)
• Finally, does it continue to work for both partners over the years?