in general they either work or they develop a fault after years of good service and die very quickly after, and its very evident as you drive, the wheel spends a greater proportion of the time NOT on the road surface.
physical damage, corrosion and leaking oil most obvious issues, gas charged shocks still have oil in them which will leak out....
and yes you can have perfectly good dampers with absolutely ruined bushes/rubbers at the mounts.
obviously if you fit dampers that are too long or so widely out of specification that you bottom them out. you can destroy them very quickly. suspension should be on bump stop before shock meets end of travel.
ie cut down springs with a standard mcpherson strut inserts don't last long
we don't have that to worry about....
spend to match your upgrades and driving ability/style/intended use
i have little ability no style and my intended use is driving to shows and the occasional squirt down the track so i buy more or less standard stuff and i still think of my 15 year old shocks as my new shocks....
cars has done about 10,000 miles
KYB gas ad-just are not considered a performance shock, jack of all trades and potentially master of none, but fit in the place where a standard shock once went and are an obvious seat of pants upgrade over anything that was worn out before. KYB, japanese company that makes its money making shock absorbers for planes and plant/machinery, never gonna be refined but do a decent enough job, plenty do it better but bang for buck (a set of 4) i'm happy with what i got, and will replace when they are noticeably degraded.
car run at a ride height that follows chrysler australia track spec. i.e lower than your average A body passenger car, but very much not on the bump stops at the front, correct wheel diameter and tyre side wall height. nothing drags on street/pavement features.
Dave
