Hi nigelh,
I do about 1/3rd of my flying with nvg.
They are great for getting the job done - but all scary moments in the last years were while flying with nvgs....
Even with proper training, nvg in front of your eyes, you are easily going further than you should. (
There are dangers, which will surprise you without proper training.
Take a big chimney with lights in front of a city.
You having a little decent - going straight for the chimney - and you might misinterpret all the green lights as streetlights....
Take rain or snow - you won't see the drops - only recognize a reduced visibilty. Until with snow - you suddenly find yourself in a black hole.
Take a nice flat landing site - until you touch down and find out, that on grassites you might not see the slope until you switch on your landing light - which might blind your nvgs....
Proper training is required to know about all the dangers - and even with nvg, you should stick to the normal VFR-Night limits - or you should have a really good reason, to risk your own and your crews life i.e. saving another life.
Greetings Flying Bull