I got great advice on the same question related to shocks.

Shock longevity: mileage Vs age ?

I decided to change the four shocks. They were relatively cheap and the outcome could'nt be better.
Now I am wondering on the very same issue but focusing on the springs instead.
What do you think ?
Will springs outlast shocks or should they also be replaced based on a double entry table: time / mileage ?
Of course I am speaking of springs with no evident problems. The discussion is not about broken/not broken but about ride/comfort IF replaced.
Thanks, Jorge

the clk crack I just found on the left rear, 92,000 miles; the ml had 135,000 miles when the spring went (rear right side)

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87 300e (white/black; amg body kit)
88 300ce (red/cream; amg body kit)
93 300ce cabrio (white/blue/blue top)
93 300ce cabrio (black/grey/black top)
98 ml 320 (totaled @ 137,000 miles)
99 clk320 (black/grey/black top)

Richard,
Your points seem to define that NORMALLY springs outlast shocks.
The "core" of my question, however is: lets say I have a car with 90K miles on the clock. No cracks at all related to springs. So no NEED to replace. Now the question:
If I do replace the springs will I get a far better car (as it happens with shocks) or no improvement in comfort/handling will be perceived? (thus pointing to: don't change if it is not broken)
Thanks, Jorge

Normally springs last the life of a car. There are some things that can cause this to not be the case - such as on my Jeep, where excessive weight and the small leaf springs resulted in sagging - but there is no need normally to replace a coil spring if it's less than 20 years old, aside from it being broken.

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Current:
2021 Charger Scat Pack Widebody "Sinabee"
2018 Durango R/T

Previous:
1972 280SE 4.5
2014 Jeep Grand Cherokee Limited "Hefe", 1992 Jeep Cherokee Laredo "Jeepy", 2006 Charger R/T "Hemi"
1999 Chrysler 300M - RIP @ 221k

I had one of the springs measured from the '86 SDL. The spring rate was unchanged at 340 even after 20 years. They did determine that the load height had decreased by 1/2" in that period.

So, the only reason to change the spring is to increase the ride height, and, that's only when you don't have any thicker factory spring pads available. The SDL is in this situation.

Many thanks for your advice.
Now I know that I have nothing to do with my springs and that by going this way I am not losing anything.
This forum is GREAT!!!
Jorge