She did Sweet Charity in Vegas for six months, followed by a week in Los Angeles, and she also did six-and-a-half months of Charity in London, which probably counts, though just by a week or two, as her longest run in a lead. The Las Vegas production was a tab version of the show, performing twice nightly for most of its run, so she did more performances of the role in Vegas (albeit in a 90-minute version of the show).
Her longest run, albeit in a supporting role that was really just dancing, was probably in the London production of Kismet early in her career, but I don't think you're thinking about things like that. Perhaps she really didn't like doing long runs. She got great reviews for Sweet Charity in London, and it ran another seven months there with Gretchen Wyler, so she clearly chose to leave.