I spent quite a few hours wearing NVG during my RAF SH days. Initially, a few years prior to GW1 we trialled flying with "PNG" (Passive Night Goggles) which were designed for earthbound use, not for flying. One eyepiece had to be focussed inside on the instruments, the other outside because they were built onto an olive green, opaque plastic faceplate and you couldn't see round them - crazy, dangerous days. The Gen 1 NVGs (actually designed to be flown with) that came later had a battery pack which Velcro'd onto the rear of the helmet and acted as a counterbalance for the goggles themselves, which clipped onto the front.
I later went to a fixed wing tour where NVGs weren't used. On my return to SH (initially to refresh for GW1) a later generation of NVGs had come into use. They had built in batteries and therefore no separate pack. Because of the internal batteries they were heavier than Gen1's.
I was hurriedly issued with a set and expected to just get on with it as it was known that I used to be qualified and instructed in their use. I fitted them and found them really, really uncomfortable. The only way to prevent the weight of them pulling the brow of my helmet right down was to tighten the adjustments of the liner right up, until my head and neck really ached and I could hardly see. It was a long night and I certainly wasn't at my best! The second night I flew with them I was given a different set. I then realised that the set from the night before was missing a heavy lead counterbalance weight that was supposed to go on the back of my helmet....
And yes, these days I do suffer from quite severe neck problems (so does my wife, she says since retirement I'm home a lot more and I'm often a pain in the neck).