I don't think OKCupid contains a good way of tracking long-term romantic success once a relationship escapes from the site, but it certainly has the data to correlate any one of several personality metrics with length of correspondence, which strikes me as a half-decent proxy: there's a huge library of personality tests on the site, including some well-known ones like the MBTI and the Big 5. OKTrends has almost certainly touched on this before, although you'd probably have to apply a lot of logical glue yourself to get a theory to stick together properly.

OKC's primary metric, however, relies on self-selected answers to a large pool of crowdsourced questions. If there's been any academic research done in that exact space I'm not aware of it, but it wouldn't be too much of a stretch to view correlations between match metrics and actual romantic success as answering the question "how well do people know their own romantic preferences?" -- or conversely to see academic answers to that question as informing OKC's methodology.