You're right. DUH.
That spring is a flat spring. I must have been thinking about the trigger return spring that failed in my Glock 17 when I responded. That was a
coil spring, and it works like most coil springs -- by being stretched (or compressed) and then returning to a relaxed state.
The following image may not be the exact same spring, but it's the same TYPE of spring as was mentioned earlier.
That said, spring metal is spring metal, and springs tend to fail in the same way -- but WHERE the spring is used and HOW it is "worked" affects where (and whether) he wear is concentrated in one area or over the body of the spring, and that in turn determines whether the spring is more likely to soften (lose tension) or break before it can stop functioning.
Flat or coil springs in a trailer or car's suspension may continue to be used despite their sags, until the spring breaks. The car isn't really RIGHT, but it can still be driven. Failing coil or flat springs in a gun will generally keep the gun from working properly BEFORE the spring BREAKS.
Either way, it's micro-fractures in the spring material that lead to a malfunction. In the examples that prompted this part of the discussion, the failure sounded more like a failed spring than a failed gun design -- particularly since it doesn't seem to be a COMMON or wide-spread type of failure.