Weapons springs get cycled at high rates which can affect them. Mag springs don't. All they need to do is offer enough pressure when fully loaded to force the column of cartridges up and present a new round before the bolt comes forward in the cycle to strip it off.
The faster the bolt, the stiffer the spring to some degree, along with the size of the cartridge.
As for them "taking a set," getting weaker the first few times they are loaded, etc., it's been a long running argument on the net. Some will say it can't happen with a properly designed and manufactured spring, others can cite anecdotal experiences for paragraphs where it did.
In the long run however most mag springs don't get weak over time. The concern comes from those who want to keep a few ready at any time for action. A good example of that are the millions of magazines loaded ready to use by LEO's - and they don't all carry Glocks. It's not a problem, cops aren't buying special mags, and the internet isn't full of stories about them having malfunctions and dying as a result. It is a non issue in the big picture. Accuracy and an overabundance of team firepower injuring innocent bystanders is the big issue these days.
People like to tinker with mags, the problem, especially with military mags for the M16, is to recognize very few will crush a defective one. They will buy a new spring and follower, tweak the feed lips, and get it running - or sell their defective ones to someone else and let them deal with it. If you are buying used mags - buyer beware. Expect issues and if you get good results you beat the odds.
0.3+ is far more common for cam lobe lift--but the spring is usually compressed 50% more by the rocker arm. Chevy Duntov 099 solid lifter cam, 0.5" lift. Around 0.6" valve lift, you get somewhere near crash, if not already there. 
