I too have noticed consistency issues with Schwalbe tires disproportionate to their price. But generally their designs are good, puncture protection is effective, and wear life is long (largely in return for the hard "plasticky" compound, I think).I'm no friend of SCHWALBE tires. They pose as German's, but the majority of their tires are made in Indonesia.
They have a few top tires in the high performance line, but most are overpriced Indonesian crap with high tollerances and often plastic like rubber compound. Some of their tires are considered dangerous in the wet, but they last very long.
Very good marketing, low quality product. If you change from the average Schwalbe to a Continetal, Michelin or similar, the difference is very noticeable.
By comparison, Continental tires tend to wear out faster, like for like.
I think the sweet spot for quality, durability, and value is occupied by brands like CST (not their low priced Cheng Shin line nor their premium priced Maxxis line) or mid-priced ($25 to $50 retail) offerings from Kenda.