I believe that the common misconception is that a spring at rest, or a spring under load, is being worn, when in effect they get worn out going from one condition to the other, over and over again.
If the weapon is cocked and you are not cycling it through fire, or constantly dry firing it, day after day I would say to check it once a year, or after a range session, and if it looks worn or appears to be soft, replace it.
Same question comes up all the time with magazines and leaving them loaded. Lots of testimony that of mags sitting for years fully loaded without a hassle.
Plus spring quality today is pretty damn good, so I think you are fine to be honest.
And if I am wrong, BELIEVE ME, someone will be along with a link shortly after this post bumps it back up to the top of the list.