My longest flight so far was 5:30 in a SGS 1-26. I didn't go anywhere; it was just to satisfy the Silver-C duration requirement.
One of the longest glider flights on record was also in a 1-26, out of Hawaii: 36 hours.
I remember reading about the Nevada endurance record in Flying magazine. Like treadigraph says, I doubt that it will ever be broken!
And of course, let's not forget Dick Rutan and Jeanna Yeager's 1986 non-stop globe-circling flight in the Voyager: 216 hours, 24,986.727 (nautical?) miles