Several people carry there spare magazines -1 or store the magazines that they are not using at the time unloaded. They do this because they believe that this relieves some of the stress that is put on the magazine spring by not having it fully compressed. Stress on magazine springs is caused by constant compression/decompression I.E. actually using the magazine for range time or constantly loading/unloading.
This actually makes perfect sense if you think about it for a second. Take a normal spring of any sort and set it under an object such as a book to where it is left fully compressed. You could leave it in that manner for years and when you finally removed the book to where it is only decompressed once, there would virtually no difference in the compression rate than the first day that you had put it under the book. Now if you were to take the same spring and compress/decompress it constantly as if you were playing an accordion, it would last a fraction of the time.
The springs that I let the engineers use were single stack Sig, Kimber 1911, Chip 1911, Glock 36, and Springfield 1911, double stacked Springfield Xd45, Glock 30, Glock 21, Vietnam Era GI mag, Promag Ar 15, Magpul Gen 1&2 Ar15 30 and 20 round mags.
Something to take into consideration, all of the magazines have been manufactured within the last 50 years. If you have a early model 1911 with original parts or some other antique type firearm than you may want to do your own research of replace the OEM parts with more modern springs that have been manufactured more recently. The way that metal has been shaped and formed and what it is bonded with to make more textile has evolved over the last 100 years. So it may have been the case in the early years of magazine fed firearms to have to take precautions to make the spring last, it really doesn't apply to modern firearms. Also, where you store your mags and ammo plays a big role. If you bury them on the beach next to saltwater then naturally there will be some corrosion (or carry it on your persons with salty sweat daily) compared to storing them in a safe with a humidifier. Ammunition and the magazine springs are metal which is still susceptible to natural elements. If you are ever in doubt switch them out. Most individuals with any mechanical inclination can change a magazine spring especially with the invention of YouTube being used as an aid.
Even with these findings it would be smart to know that everything has an expiration date. If you rotate ammo, use your mags at the range, or any other function that will make the spring compress/decompress you are putting wear and tear on the spring, but if you are like me and have 30 Pmags laying around loaded to capacity for the family to grab for whatever reason, you don't really have to worry about a FTF or other malfunction due to a bad spring unless there was already a flaw in the spring/mag (which is always a possibility even with modern manufacturing and QA).
Now you know and knowing is half the battle
