The plastic piece with the hooks is replaceable. You can also buy better quality O-rings. The better O-rings look to be made of silicon. I own both the rubber and the silicon types but I've never seen any of the ones I have fail by breaking. The silicon ones just seem to grip better. I have had one of the plastic hook/base mounts break before but that was on one of the cheaper lamps I bought through D/X. Since it happened while mounting the lamp to the bike it wasn't a problem as I had extras.

You can buy all the stuff I mentioned through ActionLED. They also sell nice alternative mounting solutions ( bars and helmet ) for the MS/MS clone type lamps as well. It you don't like the O-ring mounts the lamp can easily be modded with one of the ActionLED mounts.

Personally, I have no problems using the O-rings mounts but with heavier lamps the O-ring mounts simply can't provide the tension needed ( without additional modding ) to keep the lamp in place.