Shoot it till you have problems. I recently sold my son my Glock 17 after getting the SR9c. That Glock had over 20,000 rounds & I had never replaced anything. I put a new 2lb. heavier recoil spring in it out of guilt & the felt recoil was much better.
My suggestion is, if it will make you feel better, order 1 from Ruger, their only about $5 for the whole assembly. Otherwise, you will know when it's weak, it will eject the shells a LONG way.
Thanks, I am not as much worried as curious. I have seen where some gun companies like Kimber for instance don't think you should keep a spring as long as I have had mine. I know others like you that have kept the same return spring for thousands of hours. I will probably shoot it until it fails.