Relationships aren't like airplanes
I iterate on everything. I've given up the bulk of my planning phases because I know things will change so much before I finish that I'll omit huge chunks. I start. I fail. I fail again. Eventually, I learn what I'm doing.
When trying to achieve flight, the wing shape was a crucial component to consider. But designing a wing, flying a plane, crashing, and then making repairs took weeks to months per wing design. The Wright brothers sped up this process using a windtunnel. With a windtunnel, they could test several wing designs in days, ultimately leading them to their successful airfoil design before anyone else.
Not only were the brothers clever in their wing design testing, they were also skilled repairmen. They built their engine in such a way that they could fix it in the field so they never had to make multiple trips to their bicycle shop.
Speeding up the time to retest is crucial for incremental progress, so why can't I use this in relationships?
Iterative relationships take a few different forms, some people try to date the same person iteratively, but I'm concerned with practice relationships. A practice relationship is one that encourages experimentation, but without worrying about the consequences. The goal is to improve future relationships, because you don't want to mess anything up when it matters.
But when it matters, when a relationship really matters, you're emotionally invested. Emotions act in a way that any prior emotional training would be useless. It's one reason many public speakers say they still get butterflies before their speeches, regardless of their years of practice.
Even if we assume practice would help, then practice relationships wouldn't be the way to train. A forced relationship involves very different emotions than a serious one. Even physical interest is warped by real emotions in serious relationships, making all aspects of the practice ineffective.
I'm not advocating for people to stop dating for fun; I'm not planning to. However, dating someone shouldn't turn into a relationship if the intent is to practice for something meaningful.
Wright brothers info: http://neurographs.wordpress.com/2011/02/04/fail-fast/