If Kahr's spring regularly breaks, you might contact Wolff Springs. Click on: Wolff Semi-Automatic Pistol Springs - Magazines, Recoils, Hammers, Firing Pins & More
See what they say.
They probably have a better-quality replacement spring available, and they can give you better advice on service intervals than can Kahr.

Since I have and carry a CW9, I was understandably concerned about this issue, so I called Kahr and spoke with them. They were very insistent that they do NOT have a spring breakage problem with their guns. They said that it's quite possible that a spring could break. Any mechanical system can break. But they assured me that this would be an isolated event and not an ongoing issue with their guns. They did confirm that they "recommend" that if the gun is going to be used for critical use, in other words, self defense, the recoil spring should be replaced every 1200-1500 rds. But they said this is simply a preventative maintenance step, to ensure that the spring does not weaken with repeated use, as any spring can, which may cause the gun to malfunction. It is not due to concern over spring breakage.

I find it interesting that 15 years later that Kahr stated it doesn't have a problem. I find it even more interesting that they STILL recommend replacement every
1200 to 1500 rounds. Does anyone recall any other company with that soon a replacement, or for that matter a replacement at all ? If one breaks on your
weapon you will feel as I did... sick to the stomach and not trusting it to the point of not carrying it except in your vehicle on the drivers door where you keep
your maps..... so if there isn't a problem why don't they recommend changing all the springs in their handguns as a defensive posture against failure ? As you
said they stated " a spring can break ". Cop-out.. Perhaps they should call some of their former employees and take a refresher course. I'd be happy to
furnish my name and serial number of the weapon if they would like to check their books.

To be truthful, some guns exhibit more symptoms of stress than do others. Shortie semi-autos always exhibit signs of stress, because their recoiling parts are, indeed, comparatively highly stressed.

Also to be truthful, my two full-size Government Model .45s have been using the very same spring set that they were delivered with. This is after more than 20 years of competition use, and lots and lots of practice. But the parts of well-designed, full-size guns are not particularly stressed.
Just after the end of WW2, our government ran a "shoot-'till-it-won't" test upon all of the pistols of the war's major participants. The test was reported in detail, in an issue of the American Rifleman, probably during the early '50s. (I read it, back then, but I don't remember the date.)
Every pistol dropped out with broken parts, some quite early in the test, except for the US Government Model .45. The .45 did suffer one stoppage during the test, but that stutter was attributed to the extra-long thumb of one of the testers, which had been pressing upward against the gun's slide stop.

You're right on the money about the stress on compact weapons. Isn't it interesting Kahr only seems to be interested in the slide spring ? And that's why I
posed the question if anyone had a similar issue. And as far as that goes other compact weapons as well. Are those companies recommending similar spring
replacement at 1200 to 1500 rounds ?

Since I was reminded of the spring failure on my weapon when I joined this forum I decided to dig out my paperwork on my weapon and subsequently
recontact Kahr arms. I learned quite a bit and now feel more informed about the incident. It seems my K-9 LadyK had a different recoil spring in it from the
factory instead of the ones currently being used. While it was technically a refurbished weapon ( explanation was a total inspection and replacement of parts
returning the weapon to a new condition ) If indeed the weapon had the recoil spring replaced just before I bought it, it failed after several hundred rounds
which is an even greater cause for concern. Easy to understand the logic of changing of the type spring that was used. He also stated normally the weapon
becomes unreliable but he's never seen a spring actually break. While I accept him at his word, I did have an upturned eye with that statement.

Bottom line : tech person offered to replace my recoil spring to make sure I have the newer type, no cost. He stated that if I had FTF and FTE ( I had a
couple ) that this should resolve that issue. He also stated since I was obviously not told the truth about the weapon he would work with me if a warranty
problem comes up in the future. Still slightly troubling was the suggestion that they be replaced at the still recommended 1200 to 1500 rds. However, if this
spring change makes the weapon totally reliable after I fire a couple hundred rounds I will probably start carrying it again.
When I dug up the paperwork it was manufactured in 1996, sold to me in early 1998 and sent back to them for repair in 1999. From 1999 to present I doubt
that 300 to 400 rds were fired from this weapon. So, I'm going to give it another go with the newer spring and see what happens..