hi there Sharp, don't take this the wrong way, but it really seems that its you thats the constant factor in all these tire shinanigans. I really do think that not noticing that you are running over stuff and/or getting bits of stuff stuck in your tire and not noticing and so the shard works its way deeper and deeper, doing more damage as it goes.
I tend to try as best as I can to keep an eye out for glass etc, and when I do run over it, I always stop and take the minute to run my finger ovr both tires and dislodge bits that once in a while do stick in and would have caused a flat and or more damage to the tire with time.

I certainly notice that when I commute much more in the dark, spring fall, I tend to get stuff stuck in my tires a lot lot more often, and Im convinced its because Im just not seeing the stuff in the dark/dark+wet. Now of course having a nail go through a tire or a piece of metal is a whole diff story, and I've had these happen too, but you know, I have also noticed over the years that into my 50s, I dont notice stuff as well as I used to, ye ol eyes just arent as good as they used to be.

I guess in the end you are certainly riding through areas with bad debris, and if you managed to do in a marathon plus tour---yowser, thats a pretty damn tough (and heavy) tire, so this kind of shows the stuff you are riding through.
Hope you can stop being the tire killer, must be frustrating even if a certain amount of it must be operator error. You are certainly collecting quite a list of tire types that go RIP.....
cheers, and I hope you aren't put out.

ps, how was glass and other road debris overall on your trip this summer?