Another False statement
Simple Metallurgy
Tempering: is usually performed after hardening, to reduce some of the excess hardness, and is done by heating the metal to some temperature below the critical point for a certain period of time, then allowing it to cool.
Springs: Under tension for an extended period of time can become weaker. Springs are specifically designed to contract under load in order to absorb energy from outside stress, then return to their natural state when the load is released.
Spring Fatigue: Over a long enough period of time, fatigue can occur, which is a condition where enough stress has repeatedly acted on the object and some deformation becomes permanent. In this case, it is harder to regain its complete normal shape. This is essentially what happens when a spring wears out. Any corrosion on the spring will advance this condition.
While your Plainfield sits in your closet for another 4 or 5 years, with the action closed. You only have 2 Springs under partial load - The Op Slide Stop pin 'Friction Spring' and the Trigger spring.
Obviously you've never turned the crank on a old motor to relieve / alternate the pressure on valve springs. Ever measure a old valve spring next to a new one ?
Ever sleep on a steel spring coil mattress ? If not go try it, the local dump is full of them. Why would those springs go bad ? The answer is from extended compression leading to fatigue.
Temper, The way a smith or manufacturer would temper steel or other metal, was to improve the hardness and elasticity by reheating and then cooling it. When it ages you have metal fatigue and loss of some elasticity, known as 'Creep' / 'Memory' to those who know. Any bending, distorting or kinking of the spring will hinder elasticity also.
In TM9-1276_1947 ,
Every spring has it's ID, OD, Free Length, Number of Coils, Mean Assembled Height, Load at Assembled Height, Operating Height, and Load at Operating Height: Measurements, Lengths etc. Listed.
Page 35, Section 25 Under
'Inspection and Replacement of Springs' Covers Inspection and Replacing the Springs.
The Overhaul Chart describes Inspection and Upgrading Springs.
These are recommended Repair, Replace, Inspection and Rebuild guidelines for 5-6 year old Carbines.
TM9-1276_1947:
http://www.90thidpg.us/Reference/Man...-1276_1947.pdf
Best to store your action with the Hammer, Bolt / Op Slide forward. So the Compression load is off most all the springs.
I wouldn't recommend leaving fully packed magazines for long extended time periods. Best to rotate the magazines you leave some loads in.
I posted this so you wouldn't be confused by the other reply.
FWIW