To shed some more light on this, I just learned that the longest match in Wimbledon history, in terms of total games played, was set back in 1969, with a final tally of 112 games played in one match (P. Gonzales def. C. Pasarell - time taken: 5h12m, over 2 days). The '6:33' mark which I mentioned eariler I knew was in reference to a recent French Open, but I couldn't entirely recall which contest; I've looked it up now, and see that it pitted F. Santaro v. A Clement, at the 2004 French Open, in which it took Santaro 6 hours and 33 minutes to finally triumph over his opponent.
The most famous "endurance match", though, was perhaps that of a contest between J. McEnroe v. M. Wilander, during the 1982 Davis Cup, which McEnroe eventually won, but took over 6 hours and 20 minutes to do so. Also, there were the back-to-back epic Wimbledon finals' clashes which involved the reigning "Master of Grass", Roger Federer, falling to R. Nadal in 2008, and then triumphing over A. Roddick the following season in '09. Both matches were remarked to be instant classics and extraordinary legacies of all-time greatest matches to be witnessed.
These links might have helped anyone a day or a week ago, but this match - then, here and now, continuing into tomorrow - has finally surpassed and united all the "longest" records (save for the individual courts and playing surface mile-markers).
Longest tennis match records - Wikipedia, the free encyclopedia
Longest Tennis Match Ever Continues Thursday - CBS News
Wimbledon Men's Trivia