Quoted:
I'm considering the AB Nightvision MOD3 with L3 filmless WP tubes.

Tube Matching
Do binocular devices need tubes matched with similar specs or is it sufficient to match tube type/model? Is there generally an attempt to match tubes with pre-built binoculars?

Monocular to binocular
If I first bought the MOD3 monocular, would I have any issues buying the bridge and another monocular to make a pair of binoculars?

Dual gain
Are dual gain knobs finicky? I can imagine: either doesn't require that much adjustment to get a decent image, or I'd be fiddling with two independent knobs all night. Which is closer to the truth?

If I was just hiking around with these goggles at night where there are few artificial light sources, should I go for automatic or manual? How much does gain even need to be adjusted automatic or otherwise? Would I generally be fine leaving them on one setting almost all the time?

Durability
I get that no one is dropping their $10k goggles for fun, but how do these feel in terms of durability? I know they just changed the female adapter from polymer to aluminum with the Bravo bridge. Are the optic pods polymer or aluminum?

Waterproof
These have a 66 foot submersion rating. Does this mean the unit will basically function underwater or just that they can survive submersion and will function after they have been dried out.

Nitrogen purging
Important or no? Does a retailer like TNVC nitrogen purge routinely?