Stan, my source is a structural engineer that is building an addition to our hospital. My original highlighted statement came from him and my 30 second engineering class. I then went back and explained the whole problem to him. His response was that springs when first compressed "do" shrink a little. This is called the "spring set" after that, fatigue and final failure are caused by reasons you listed above and not from extended compression. Because of the initial spring set may be unknown to the shooter it could cause a failure to feed but there are a lot of variables to figure in. My engineer believes that spring set and manufacturer quality determine if you should load or not load the magazine to full capacity. Any reputable manufacturer would be fine to load to full capacity, if there is any doubt short load it by one round until you can get a better magazine.