Andrew Gabriel presented the following explanation :
Airbags are generally rated for 10 year life, and it might
be that yours has detected that it's gone over 10 years old.
Check if the service schedule for your car expects replacement
after 10 years.

That used to be the case, it was the expected life at that time, but
now they are suggesting an indefinite life for them, or until deployed.
Have you ever found a source for replacement bags for a 10 year old
vehicle?