Like most firearms, some GLocks have went thousands of rounds without breaking a single spring of having a malf. due to weak springs. Others have broken a recoil spring with less than 500 rounds due to a bad factory spring.
I don't recall ever seeing a set time for spring replacement in a Glock. One thing you need to do as a owner is INSPECT the parts of your gun when you take it down to clean it. Look for unusual wear, metal shavings, plastic shavings, cracks and so on...anything that looks different than you think it should. If you find something, take it to a trusted smith and have it looked at.
My 2nd generation G21 is well over 10 years old, and works 100% with it's original recoil spring. I have changed some parts out in this gun, mostly due to design changes and upgrades.
If this topic worries you, go right ahead and swap springs out every 5,000 rounds or so. If not I wouldn't worry much about it for years. Odds are, if you get a bad spring from the factory, you will break it the first year.
Of my 6 Glocks I have left, none of them have less than 5,000 rounds through them...and all are working on factory original springs.
I guess the answer is - Shoot $3,000 worth of ammo, then spend $30 on new springs.
