Air Springs/Bags

[one_dusty_hoot]

While doing some other checks last night I
looked closely at my air springs. There is
no checking and the rubber appears to be in
good condition. This is a 20 year old rubber
bag!!!

Seems like the air springs came out in late 80's
or so. These air springs would be approximately
7 years older than mine but I do not hear of any
high incidence of failure reported, one or two
sure, but not many.

Is there a useful life on these? Or, time when
they should be replaced, age or miles?
TIA
bob janes, 87FC35, SC