The Indian experience in NE, the British experience in Ireland and their numerous colonies, and the French in their African and Far East Asian colonies all independently came to the conclusion that a determined, motivated and fairly well supplied insurgency could not be crushed out of existence in a short time frame. It usually takes a generation (25 years) or two of slow, dogged, unrelenting pressure to break the back of the militant movement, and sap away the motivation behind the determination. Heavy handedness generally doesn't work, unless you're willing to go the Soviet way.
This is the reason why I prefer, as do most strategists, to not use the military sledge hammer for what is essentially a slow chiseling work. The extended time period of deployments tie down precious divisions, weaken the military, and also bring with them undesirable effects on the operation itself. COIN should preferably be led by the local police, and failing that by a specialized COIN group.