I've had a GMAX GM68s for about 18 months and nearly 12,000 miles. I bought a medium because it fit well. Now, it doesn't fit correctly. It is getting loose. The cheekpads are getting soft and don't hold my face as well. The padding in the top has loosened to the point where I can now stick my finger between the helmet and my forehead just past my first knuckle. I have a HJC helmet that I'll be wearing (that does fit properly) until I can buy a new one.
The helmet is also getting noisy and the vent system on the top is starting to come unglued. It was a good helmet for one year. I guess I shouldn't expect much from a $130 helmet.