Prior to the requirement for all airline pilots to have an ATP, I gave IOE at what was then American Eagle. Most of the new hires in those days had 350-500 hours or so. Most took anywhere from 35-50 hours to finish IOE, but they showed progress each flight, so we continued until they finally "got it" well enough to be safe line pilots. In three years, I had maybe two new hires who hit 100 hours.