Learned this the hard way with stuff way beyond plants honestly. Old bottles of glue that look fine till you use them, stale gas in the mower, that jar of paint from a year ago. We all hoard things in the garage thinking they stay good forever, but stuff breaks down even when it is just sitting there. Soil goes bad, glue dries up, gas turns to varnish. The lesson is the same every time, old is not the same as fine, and the fix is always to just start fresh instead of trying to save a few bucks.

Did you ever stop and think the operator might be part of the problem here? Four hundred square feet on one pad is a lot of run time and if you are pushing the machine too fast or tilting it, any blade will dish out and chew up the floor. Cheap steel is softer, sure, but a guy who knows what he is doing can baby a bargain set through a whole warehouse pour. Maybe the angle was off or the RPMs were too high for that concrete mix. Blaming the kit right away is easy, but bad habits will ruin good blades too. Spend the money on name brand if it makes you feel better, but it will not fix your hands.