Having just spent several hours again in my field picking out rocks, I've come to the conclusion that nearly an acre of my field was used to dump schist which was dynamited out of the ground across the property to build a large building. Every single bit of rock I pulled today was schist, not another type of rock in the bunch. I always knew it was likely a dumping ground for it based on old satellite photos of the place when the building was under construction, I just didn't know it went quite so far down the hill. (Or ... it actually _is_ the hill, I think, in part).
Anyway, the thing about this schist is that if you hit it with anything it breaks into smaller pieces. Even my mattock trying to disloge them causes them to break. I'm thinking a blade that hits this stuff just turns it into successively fine abrasive material. Though there wasn't that much exposed, I'm probably making it worse trying to dig out the big surface pieces, it looks like a very large gopher has been making a home in the field.
Anyway, I hear "lifting blades" and will ask the dealer about it (i.e. the alternatives). He's saying the blades don't look abnormal and that I should get another year out of them, but I was kind of expecting more than two years out of blades for such a small field, even though I knew it was going to be a rough first cut.