"I perform ceremonies as an officiant, and know other officiants. The worst (IMHO) are the weddings that are just a bad idea. The couple is young, inexperienced, and selfish. I mean, even courthouse weddings can last decades, but if you have a wedding that is clearly not planned out, they are often not though out as well. Weddings that are rebellious as a "f@#k you daddy, I am 19 and marry who I want!" I give about 2 years, especially if the bride and groom are out of sync with one another, or one just looks like "this was the other's idea primarily."

Oddly enough, weddings with cheesy themes (Star Wars, Elvis, etc) last longer than the traditional styles. I have theories on that, but don't have enough data that's not anecdotal to back it up. But I think casual weddings where everyone is relaxed, happy, and having a good time because the wedding is about celebrating rather than ceremony will last the longest.

A sense of humor helps. If both the bride and groom are relaxed and silly with one another, those last the longest."