It is best to have as much light as possible when mountain biking in the dark. Mostly this means to have at least two reasonably powerful lamps, one in the handlebar and another in your helmet. The one in the handlebar should point pretty close to give you peripheral visibility in front of you while spotting the route ahead.
I wanted to have some easy mounting solution for my helmets and GoPro mount was an easy choice as I already had some mounts on my helmets. I started working with an J-buckle as it already has holes in it for easy screw attachments.
I then took a small piece of 20mm electrical tubing and attached it to the mount. First try revealed that there was a small clearance issue between the rubber band on the lamp and GoPro mount.
Last summer I managed to ride into a pretty severe OTB (over the bar), which resulted in a few weeks break from driving, buying knee and elbow protectors and the most severe of them all, a broken Reverb remote.
From outside I could tell that the remote had a bent piston and broken bushing. After the breakage, I could still use it a little on the rest of the ride, until it leaked too much and stopped working. The leakage resulted probably because the piston head was not perpendicular to the cylinder. Normally the bushing keeps the button level and guides the (straight) piston rod and centers it in the cylinder.
When I took the remote apart I also found that there were some scratches inside the cylinder, probably due to still using the remote after the initial breakage.