I would suggest moving him out to 24/7 pasture if in any way possible! Other than that, there is not much that can be done. There is a surgery that may help short-term (the muscle necessary for a horse to crib is removed, but it grows back after a year or two and the horse can start cribbing all over again).

a grazing muzzle might help. it's a cage like thing that attaches to the halter over his mouth so he can eat/graze and drink but not crib or chew wood.

I agree with Serena. At least, make sure he has plenty of turnout. Sometimes that's all it takes. Our thoroughbred, Gus, started cribbing when we got him. The barn where we were keeping him only turned horses out every other day and then only for a few hours. We moved him to a different barn where he's out most of the day, every day, weather permitting, and the cribbing has disappeared completely!

Though I agree 100% with Serena and Patricia...if that isnt an option try hanging toys in his stall so he has something to do...and give him extra hay it might keep him busy.

I would use the metal muzzle, not a grazing muzzle on him when he is inside. I would also get him turned out more if possible.

I would give him toys to keep him busy in the stall and turn him out as much as possible. If he's been doing this that long you may not be able to get him to stop completely, but give him every opportunity to change. Simple toys could be something like old shoes tied onto the stall wall with twine or make noisemakers out of clean laundry detergent bottles with different things inside and the lid glued on (I would tie it up). Or even a Jolly Ball or Soccer ball.