All magazine springs are subject to fatigue, some magazines can go for years fully loaded and still function. Common sense tells you the less rounds in the magazine the less fatigue on the spring. Go to Wolff springs Q/A and they give a good take on the issue. I've personally have had magazine springs go for a year w/o a problem, but eventually they will fatigue and give you a malfuction. I've had this occur in AK mags and pistol mags.