When you notice them deteriorating
I have many semi autos that I have left the mags loaded to the max for close to 15 years now. When I practice, they get relief. That is what they were designed for in my opinion. When I notice feeding problems, I will look at changing the springs, but until then they are all loaded and ready to go. If a spring is going to break, it will either be instantaneous or it will weaken over time and give you notice.
I keep one in my bedside safe with a spare mag, round chambered and ready to rock and roll. My everyday carry piece is up on my credenza still with a round chambered, ready to go. All the rest are in the gun safe with a magazine in place, but no round chambered, and back up magazine sitting underneath it. Two revolvers are there also with all chambers loaded and speed loaders next to them as well. None of my long guns are stored with rounds in them, but my Minin 14, AR and AK all have mags loaded and sitting by them in the gun safe.
As for unsafe storing a loaded gun, rule one - treat every gun as if it were loaded until you yourself verify. I live by this rule and have drilled it into everyone in my house. My wife stays away from the semis because they don't interest her, but she has two revolvers and loves to shoot and knows how to clear the weapons.
By the way, it is actually easier on a lot of semi's now to see if they have a round chambered. A lot of them have chamber indicators when a round is chambered. You really can't know by looking at a revolver if there is a round "chambered" as that chamber is centered on the barrel. It is actually the next chamber that would be the hot one. Awww, but which way does the cylinder rotate, that is the question. I have three revolvers and one rotates the opposite direction as the other two, so looking at it from the front, if you don't remember which way it rotates, you can't tell if it will be loaded or not when you pull the trigger.
Just a couple more pennies in the discussion.
