The magazines held up very well. I did have a few failures to feed around the 42,000 round mark. This is when I replaced the springs and did the little rebuild (recoil spring, firing pin, firing pin spring, extractor, extractor spring, etc.) at this time I also replaced all my magazine springs in the main magazines I was using all the time. I would say given the cycle speed of the PX4 Compact, having weak magazine springs could have been the reason for the failures to feed. Meaning those rounds have to get up in front of the slide very quickly to feed correctly. I have had no issues since.
These are three of the original magazines that I got with the guns from Beretta. They have been run hard and springs replaced once. Of note is the top two mags with the plus two bottoms from the full size 20 round magazines. They were run the most out of all my mags as I have four set up exactly like this. You can see where I cut the corners off the front of the magazines to make them easier to load, kind of like MecGar mags.
I had much fewer rust issues than I thought I would have. Just a little here and there, not as much as I would expect from a blued steel magazine. More so in my carry mags as my body sweat would get to them more than my training mags.
I plan to have these mags NP3 coated and keep using them.