Many hardwood sawlogs are cut to 9' to allow for trim allowance; at minimum, cut your logs to at least 8'6" (eight feet, six inches). HOWEVER, longer log lengths (10's, 12's, 14's) and shorter log lengths (6's, 7's, and 8's) are indeed desired and purchased by mills and log yards in order to meet domestic and foreign market demands.
Longer logs frequently command a premium price, so PLEASE make sure to contact local log buyers in order to find out their exact log-length specifications for individual species and log diameters!