It's entirely dependent upon both the difficulty and the relative risk of the climb. The Edge at Tahquitz Rock [1], at "merely" 5.11a (R) has seen far fewer ascents than most 5.14 climbs. Similarly, the Bachar-Yerian at 5.11c (X) [2], it's seen, what, < 30 ascents?

[1] http://www.mountainproject.com/v/the-edge/106105353

[2] http://www.mountainproject.com/v/bachar-yerian/106244878

EDIT: good account of a repeat of the B-Y here:

http://www.supertopo.com/tr/The-Bachar-Yerian-A-Three-Year-O...