Happily unmarried: first comes love, then comes ... well, nothing. Cosmo looks at why more and more couples resist walking down the wedding aisle.(COSMO NEWS)

* With Hollywood marriages disintegrating faster Paris Hilton's wardrobe, many of Tinsel-town's most levelheaded lovers have sidestepped matrimony and elevated their status from boyfriend-girlfriend to life partners instead. Among the new nonmarrieds: Cameron Diaz and Justin Timberlake (together more than three years), Charlize Theron and Stuart Townsend (five years), and Jewel and Ty Murray (eight). Even parents Johnny Depp and Vanessa Paradis (eight) and Angelina Jolie and Brad Pitt (two-ish) have skipped the aisle walk.

But it's not just celebs. This is one trend where stars are actually following the masses instead of vice versa. "Being together without marriage has increased for decades," says Dorian Solot, cofounder of the Alternatives to Marriage Project and coauthor of Unmarried to Each Other. "It's more common and accepted than ever." In 2005, 4.9 million unmarried, opposite-sex couples lived together--in 2000, just 3.8 million did. These aren't all twosomes living together prewedding--in those same years, the number of marriages actually decreased. But long-term commitment is about more than shacking up. "It lets couples define their relationships how they want," says Solot.

So why is wedding lust waning? For a ...