This is a long, wonky post. I have a special interest in the history of vehicle safety systems. Apologies in advance for the pedantic nature of this reply.
I researched the early Porsche airbag system in great detail when I purchased my 968. Attached is an outstanding PDF which summarizes the design choices made by Porsche. The 968 has first-gen airbags with problems inherent to those systems - but the system is very excellently designed and, if operating properly, is as safe as when the vehicles rolled out of Zuffenhausen.
The airbags themselves have a very long service life and do not need to be replaced/deactivated unless there is another problem with the system.
There is no Porsche recommendation as far as timeframe for replacement. Other manufacturers vary in terms of their recommendations. MB requires pre-1992 airbags be replaced at 15 year intervals - but have stated that from 1992 on, Mercedes airbags have no service life limit.
Per Porsche, periodic dealership inspection (every 2 years) is recommended; however, the dealership "maintenance" involves only a check confirming that the airbag warning light functions and a visual inspection of the system. Otherwise the system is presumed to be operating as intended.
The SRS system completes an auto-diagnostic every time the car is started. The airbag light comes on and goes out in 5 seconds? That's the auto-diagnostics checking out OK. That's pretty much all that needs to be done as far as maintenance on these cars.
As noted in the attached article (which, again, contains quite excellent information) the 1st gen Porsche SRS requires complete replacement of sensors, control unit, and airbag module in case of deployment. All parts are still available new from the dealership- but are staggeringly expensive.
The 968 system is front-impact only. There are no side-impact sensors. There is a safety system in the control module which prevents accidental deployment when the car is stationary. There must be a rapid deceleration for the airbags to deploy - they are very unlikely to just go off randomly. It's actually a fairly sophisticated system, for the era. Even though they have some years on them, the Porsche engineers knew what they were doing and the airbag system is well-designed and robust.
Looking at the available data - both from the NHTSA and additional studies - the safety profile between first and second generation airbags IN A COLLISION - for "normal sized" adult drivers - is pretty much identical. The studies I looked at showed about a 1.5% absolute reduction in risk of death with second generation vs first generation airbags - a statistical wash. There has actually been some debate that second-gen airbags - introduced around 1995 and depowered mainly to reduce risk of injury/death for children - are LESS safe than first-generation airbags in a serious crash. One study showed 46% INCREASED risk of serious thoracic injury (related to the crash, not airbag itself) with second-gen airbags as compared with first-gen units.
That said, the NHTSA has been pretty clear that the risk of injury from the airbag itself is definitely higher with first-gen vs second-gen airbag systems (which our system predates). Between 1990-2003, there were 54 known driver deaths due to first-gen airbags - over 259 million vehicle years - or about one death due to a first-gen airbag for every 5,000,000 vehicle years. By comparison, between 1995-2003 there were 27 known driver deaths due to second-gen airbags (non-SLED plus SLED-certified) over 529 million vehicle years - or about one death due to a second-gen airbag for every 20,000,000 vehicle years.
So from an absolute perspective, second gen airbag systems are about four times safer for the driver in terms of harm from the airbag itself. BUT - they may not protect as well as the older first-gen airbags in an actual serious collision.
From a relative perspective, the driver is very, very unlikely to be seriously injured or killed by the 968's airbag. You'd have to own your car 5 million years, on average, to have a fatal event because of the airbag. Few of us will own our cars that long.
It's not even worth worrying about.
In terms of harm reduction - with first-gen airbags holding the wheel at 9-3 instead of 10-2 is actually quite important. As is maintaining at least 10 inches of distance between the driver and steering wheel.
The passenger airbag is more problematic in our cars, because there is no way to safely disable it and because it points directly forward out of the dash. No child under 13 should ever - EVER - be in the front seat. I would consider 5'2" to 5'4" to be the height threshold for allowing a teenager or adult to sit in the front passenger seat. And - my personal opinion - the passenger seat should always be positioned all the way back, at all times, whenever anyone is riding shotgun.
This is all just based on my internet research - I don't have any actual training or experience in this regard - so please just take it all as my opinion.
