The ride leaders in my club go through keeping rides together constantly. My gf and I usually do the B ride which always includes some significant hills, lasts about 35 mi. on a Weds afternoon or 40-50 miles on a Sat. morning. Our rides tend to be anywhere from 14-18 riders and we average 14.5-15 mph. Although we don't have a lot of issues the ones most likely to arise are keeping the group together and not letting the racer wannabes destroy the group by riding off the front. One ride leader who is an ex-racer (about 50 yrs old) solves the riding off the front problem by warning people that if they take off he will turn the group at the next road and they will find themselves riding alone. The ride leader has to ride from the front and really needs a lieutenant for larger groups.