I suspect the old Beldin foil plus braid is better than made in China
quad-shield. Yes, quad is more about leakage than "infiltration".

I didn't want to go into this because it gets complicated, but I buy dry
air from scuba shops. You need your own tank. Air is cheap. Inspections
are not. Tank, hose, regulator and the nozzle set me back $50. When I
blow the dust of out something, I don't hit it with refrigerant, which
is what canned air does.

The tax laws regarding buying compressed air are interesting in a
bizarre way, not that it makes much of a difference in price. If they
compress the air at the shop, that is a service, and it has one tax
rule. If they get a big tank of compressed air and use it to fill your
tank, it is stored inventory, and the tax rule is different.

I have no idea what it takes to keep nitrogen at home. I'd have to
research where to buy it. The only nitrogen I ever used was bought by
some corporation and it was the mad scientist liquid type. All that
said, since nitrogen isn't being used in life support like scuba air, I
think it would be relatively cheap.

NEMA with desiccant inside is used a lot, so some people think sealed is
fine. I have no surveys to back this up, just personal observation with
a very limited sample.

On some GPSs, the weep hole is visible. It has a membrane valve. A
friend got this brilliant idea to seal up the weep hole. He took a trip
in an airplane with the GPS and the keys got sucked down due to the
pressure change. Sometimes when I go camping, I can't open the ammo
cases because the pressure change has sucked them down. So yeah, sealed
isn't all that good in some situations.