As an aside, I now have 900 rounds through mine (No failures of any kind BTW)
Most of my current 9mm ammo usage has been breaking in the SR9c, so round count on the LC9 hasn't went up too much lately. But because I haven't tried to use the slide hold open as a release, it's just as hard to try and get it to release after 900 rounds as it was from day one. Pretty much un-doable on mine anyway.
So at least on mine, round count hasn't seemed to make a difference. But again, I probably haven't tried it more than two or three times and that's generally only after reading posts concerning the subject, just to see how mine reacts.