Though Posh and Becks are often ridiculous, I love this aspect of their coupling. In any long-term relationship, it can be very easy for two people to unconsciously hold each other back: into certain roles, looks, or behaviors. I think this subtle suppression is a big part of why marriage sometimes gets a bad rap. Staying open to a partner's changes, from hairstyles to jobs, is something that most of us have to actively work on.
The Beckhams have had some public bumps in the road, but they definitely seem to cheer each other on and allow each other to evolve, both in their styles and careers. And after 12 years of marriage (which seems like an eternity in celebrity-ville) they seem to be going strong.