Originally Posted by
Trakhak
From what I remember reading somewhere, what wears springs out is cycling them through a range of motion. Whether the springs are under compression or tension or neither apparently doesn't matter.
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If cycled within its working limits a spring will last nearly forever. Storing it loaded or unloaded doesn't make a difference. If that werent true, your car would slowly lower sitting in your driveway.
Springs don't change their constant (get weaker)unless distorted significantly. Otherwise they have 2 failure modes.
If stretched or compressed beyond their yield limit they won't return to their original length. A typical example is a bathroom scale that no longer zeros out after an extremely heavy person uses it. However, the constant is unchanged, so you can reset zero and continue using it. Old cars and trucks with a history of being overloaded sag for this reason.
The other mode is fatigue, whereby repetitive flexing beyond the fatigue threshold causes stress cracking and ultimately, collapse.