In reply to The Ice Doctor:
The Mammut Goretex? That's not a model. That's two brandnames.
I don't quite understand how much use you've had. 18 months of daily use, or several weeks of daily use?4
18 months of daily use, and I'm surprised they lasted that long. 18 months and I'm not massively surprised. They're a lightweight technical boot. Stuff wears out.
If you want a durable boot, it's gotta be heavier. I'd second the Manta recommendation. Very durable. Or maybe just accept that footwear is getting lighter, so wears out sooner.
Incidentally, I imagine Feet First could resole the Vertos for you.