Long, who went over 1,500 career points, notched his fourth straight double-double. Hayward Register added 20 points with six three-pointers, both career highs, for the Ragin' Cajuns (13-10, 7-5 Sun Belt).
The Ragin' Cajuns shot 49.1 percent, 10 percentage points better than the Mountaineers, and were 18 of 21 from the free-throw line to 8 of 10 for the visitors.
The Ragin' Cajuns led from the opening minute until the Mountaineers tied the game at 50-all with 16:21 remaining. But Louisiana-Lafayette scored 11 of the next 13 points. A 6-0 spurt put the Ragin' Cajuns ahead 69-57 and the lead never went under double digits thereafter.