Air bags

I think several bags on my Prevost were at least 20 years old when I sold the coach.
Could be original 44 as well.
I replaced 2 that in the rear were exposed to road debris what grind outer rubber showing fabric under. Even at that shape the bags would still hold 120 psi I tested them at.
Inspect the rubber. If you see lot of crack - replace them. If all smooth, just carry a spare. Any truck shop can replace them on the road.
Than some preemptive freaks replace parts at 25 percent of their life.
To each of his own.

Mine are also from 2004. The idiot light saying they are not working is on. That happened on a hot day in the mountains in 2015. I'll continue to ignore that fault.