I suspect that you hearing about 'a lot of failures' is a simple quantity measurement, and not a percentage measurement. When there are thousands (or hundreds of thousands, or millions) of a device in operation, there will be 'a lot' (in quantity) of failures. Failure *rate* is another matter entirely. And if you read carefully, it's fairly common for those who bothered to investigate their 'defective' pumps to discover that the only thing wrong with them was a piece of trash stuck in the pump (hardly the pump's fault).
Those pumps are actually designed for continuous duty in various non-aviation environments, so if fed clean gas, most will easily last the life of the airframe when used as a backup/boost pump.
Hey Sam, I might be wrong, but aren't you thinking about the PSO (positive shutoff) valve, and not the check valve? If I understand it correctly, the check valve shouldn't prevent flow with the pump off; it just prevents back-flow if you have a pair of pumps plumbed in parallel.