Strikes me, and has for ages now - the spring is perhaps the most critical single component - the mag' a close second.
Being designed as a pocket rocket with dimensions about minimized, that spring has to effect one heck of a compromize, with a very short length. Of course the smaller secondary one too performs a vital function but the main spring power is in the large one.
I do believe that a fresh fitted new spring
can compromize function, but probably not for very long. Equally I would also accept that a spring that had lost too much of its rate could allow the gun to get beaten up unnecessarily. It is this factor of two extremes that I think make for the changing springs recommendation - the attempt to have the gun in use during the relatively optimal phase of spring life.
From choice with new spring replacement - I would after fitting, hold the slide open with perhaps an empty case - and leave for a few hours - to get a preload set. Once that initial set is taken then I reckon we are good to go for the few hundred rounds.
Just how far I could exceed the change period I am not sure - but probably it could run well beyond the prescribed level, mainly I think because once that two coil set has taken, there will not be too much more - other than a slow possible attrition thru further cycling.
Just musing -