Hopefully, I can clear up some confusion about air bag operation...
There is no "cannister" system that contains nitrogen in your car (at least not in the air bags)...
The bag(s) are inflated with a solid propellent gas generator that operates identically to a solid rocket motor... in fact, these air bag generators are built by well know defense contractors that build missile motors. The generators "burn" extremely fast; and produce a large quantity of gases that inflate the bag.
The rub is that there's a huge liability issue for car manufacturers related to air bags... consumers expect safety systems to work reliability and perfectly all the time... no matter how old. From and engineering perspective, this is impossible... so the companies get sued.
On top of that, anyone familiar with solid rocket motors/missiles will tell you that propellents don't "age" well... the propellents crack, weep, and generally become unstable after a number of years. The military has a regular maintenance program that inspects/maintains rocket motors of all types. The worst effects seem to result from external heat and vibration.
Generally, when propellent ages, it doesn't "slow down", it speeds up. The flame path works into all the cracks (especially the space between the fuel and the case) exposing ever more surface area to burn... in worst case scenarios, the motor explodes rather than burns... not a good thing.
(anybody ready to guess what I do for a living?) :-)
As for the seat belts; they too age and lose strength over time...
The key here is that the restraint system in your car is a system. Its not just the air bags, or the belts, or the construction of the car... its the combination. Betting that one part alone will save your bacon as well as all together is not sound engineering.
Its a personal choice I guess, but $2400 won't pay for a day of intensive care, much less the cost of putting your face back together...
Just my 2 cents.
KenP

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KenP

1996 S500 W140 Coupe