Mileage may vary depending on the conditions and the amount of rounds cycled through the magazine. Meaning if your a competition shooter you may wear out spring quicker than a occasional shooter.
Welcome Chai_glock, Hey if you get a minute go over to the Introduction section and let us know a liitle about you and your glock, glocks. Pics are great too.
Glock897 - never heard of anyone who had to replace a Glock magazine spring. Not saying it never happens, just saying I've never heard of it. You can buy replacement springs for your magazines at Glock accessory websites for a few bucks. If you're concerned about springs giving out on you, it's not a bad idea to have a spare or two handy in the range bag.
I have over 50k rounds through my one mag and it is still hard to load. The key is to rotate them. Every month i empty my current mag and put it in the safe. I take the one previously placed in the safe, load it, and use it for that month. So every other month my mags get a month off.