Easily 1000 reps, maybe more? And I did use snap caps for the more lengthy sessions, I have a feeling its down to the hole in the breach face being just slightly out of spec and it was causing a non uniform impact. The striker itself did look mildly pitted so this may just been a poorly molded striker, either way its getting sold when I either get a replacement striker from Walther or after I ship the gun back and fourth between them.Very sorry to hear and see that happen to you.
It's not unheard of for a striker to break, particularly with a lot of dry fire practice. Some weapons systems specifically warn against any sort of dry fire without snap caps.
Glocks would not appear to be immune to the phenomena
Curious... how much dry fire practice are we talking about? You say about a months worth. How many repetitions might you guess that you've done in this time? Not that any particular number would justify the striker breaking but I'm curious what it took for it to break.