Shooters,
It has been said in the past to replace your recoil spring at about 5000 rounds. There is a better indicator of this need other than the number of rounds.
Proper utilization of the correct recoil spring for the load at hand and the spring's timely replacement will lead to increasing the firearm's proper function, reliability, and useful life! An out of spec spring will shorten the life of the firearm, and affect the proper cycling of the firearm, too.
The number of shots may have only limited bearing on the time to replacement of the recoil spring. Think about that for a moment. One may fire moderate to light loads, and then one may fire moderate to heavy loads. The correct spring for the load at hand will be approximately under the same stress loading at the appropriate pound rating, whether light or heavy loads are being used. Granted, one may use a light spring for all loads, but this comes with the increased spring wear and pounding of the frame of the pistol which can lead to cracking of the frame!
When using the correct spring for the correct load, spring length is the best gauge of time to replace the spring. When the spring looses 1/2" in overall length, it is time to replace it! Always use the longest spring possible, without coil-binding the system, as this best controls recoil and proper cycling of the firearm.
Upon installation, note the spring's length. During routine cleaning, note the spring's length. When it is out of spec, regardless of the number of shots, it is time to change it!
This might sound finicky, but in my shooter's bag, I carry a selection of springs, from light to heavy and install the correct one to match the load being used. They don't cost that much and will lead to increased life of the pistol and enhanced function, too!