Recently I spoke with the law enforcement representative at Sig Sauer and he advised me that a "duty weapon" should be completely disassembled and deep cleaned every year by a certified Sig armorer. That every three (3) years or 5,000 rounds, the pistol should be inspected and a spring kit installed. This includes the recoil spring, slide catch lever spring, trigger bar spring and de-cocking lever spring. The remaining springs throughout the gun will generally last longer, but they should be replaced every 10 years or 20,000 rounds, whichever comes first. The pistol's magazines should also be inspected annually and if needed, the springs replaced. If the slide won't lock back on an empty magazine, you probably need a new magazine spring.
Of all the springs in the Sig pistol, the "recoil spring" is the most important, because it protects the gun from recoil. As this spring weakens, it allows the slide to slam harder and harder into the frame sending shock waves throughout the pistol. This eventually leads to broken internal parts and maybe even a cracked frame like the one shown above. Although Sig recommends this spring be changed every 5,000 rounds, many knowledgeable shooters change it every 3,500 to 4,000 rounds, especially with the higher-pressure rounds like the .40 or .357SIG calibers. Considering how you can change this spring out yourself and it costs less than $10.00, it's cheap insurance against reliability problems or breakage on your gun.
Above is the picture of an overused 'recoil spring' and below, a damaged 'firing in positioning pin' from the slide of a Sig P220. Below, you can see how this pin was working its way out of the slide and when extracted, it fell into three (3) pieces. This pistol was on the verge of a catastrophic failure. If the deputy had changed out the 'recoil spring' after 5,000 rounds, this gun would never have gotten into this deteriorated state.
In conclusion, like any other semi-auto pistols, Sig Sauers need regular maintenance. Change the recoil spring every 3,500 to 5,000 rounds and get regular inspections by a certified Sig armorer. Don't forget about your magazines. The majority of malfunctions are generally caused by weak magazine springs or faulty ammo. You can buy these parts yourself at Internet web sites like www.topgunsupply.com or www.brownells.com. Regular maintenance is the key to reliability. It's a simple process and the best way to ensure your pistol will perform when it's most needed.