Yeah, Art, I'm a bit skeptical about these competing theories of:
A. Springs take a "set" if left compressed; and
B. Springs ONLY wear out from being cycled.
From the old Dire Straits song "Industrial Disease," it's like that line about "two men say they're Jesus. One of them must be wrong." Or perhaps they are both right, just about different types of springs and/or defects.
Qualifiers like "true" spring steel don't help much without some definition.
This much I know: A Ruger 10-22 from about 1964 production was stored with the bolt back all the time for 30 years. The hammer spring got weak and caused misfires. The replacement Ruger sent me (for free!!) was about 1/4-inch longer and substantially heavier to compress. It was a coil spring.
I suspect that the ratio of spring wire diameter to length may play a role. Those valve springs in our engines cycle a whole bunch and are exposed to heat, but they are also much thicker, proportionally, and are compressed to less than the "solid stack" stage.
Based on experience with that Ruger and one or two magazines whose springs *seemed* weak, I generally keep 3 mags loaded and the rest empty, rotating them yearly. I remember the Jeff Cooper article as describing .45 gov't model mags left loaded at the parents' place during WWII and for a few years afterward, total time compressed only 7 or 8 years.
How long have you owned YOUR house gun? How long do you plan to own it? Think about it.