My experience with 1911 springs may differ from others. After I cracked a slide in the early seventies, I became REALLY interested in spring life.
The 16 lb. spring had "sagged" to 11 lbs. over time and I sincerely believed was one of the factors in the slide failure.
At any rate, I started "weighing" springs. It is a simple matter to "weigh" the springs. Have your 1911 assembled and lubricated. Get a PVC pipe nipple of the correct diameter to rest the pistol in a vertical position with the nipple surrounding the barrel. Cock the hammer first (after checking the gun to make sure it is unloaded
), and with the nipple on a spring scale (I use an old kitchen scale), you simple press the pistol down, allowing the slide to retract with the barrel inside the nipple. Watch the slide and when it is just shy of bottoming, read the scale.
Using a full size 1911, the standard spring will weigh 16 lbs. When shooting IPSC with full power loads, I chose to use an 18.0 lb. spring along with a slide buffer to protect my slide. When using light target loads, you will almost certainly need a lighter spring to allow reliable functioning.
After you establish a "standard" by testing with a new spring(s), you can tell after 1000, 3000, 5000, or 10,000 rounds if your spring is "sagging" (getting weaker). After a loss of two pounds from original poundage, it is time to replace the spring. Springs are MUCH cheaper than a new slide, believe me...
It, of course, is quite useful to test your scale with known weights in the area of your needs. The minimizes "surprises"...
P.S. A really useful test with a new spring in your 1911, is to use your normal load with a new spring and note the distance the cases are ejected. That distance is represented by the slide velocity when the slide retracts. So, if you notice your cases being thrown further than normal, I would suggest it is time to weigh your spring (or check your loads)...
Just a thought or two...
FWIW
Dale53