Good advice from an Anandtech poster:
Western Digital BLACK or RED is a minimal consumer drive quality level to be used in any application, and anything less reliable should never be graced with your dollars. Less reliable drives lasting for years in some particular situations is largely a myth - it happens only if certain criteria are meet, namely, low loads and small temp cycling, which rarely occurs in the real world of consumer computing. When looking at Western Digital drives, always stay away from GREEN and BLUE drives, simply because components are designed to last only under certain special conditions, and I believe these special operating conditions in practical terms are just a myth. In essence these manufacturers (marketing honchos) give credence to conditions of "LOW THERMAL CYCLING", which they then decree is a significant portion of the market place, when in reality it really does not exist, and only gives them an excuse to design "only as good as needed" devices. The existence of the low quality drives permits them to charge more than they normally could for the better drives. Don't believe the hype, the more expensive drives are required for good reliability and performance.
Don't ever buy too cheap, if you want to avoid repeated disk crashes, and there is nothing wrong with periodically replacing working drives with new ones periodically to avoid the inevitable disk crashes. Even good drives eventually fail. If the manufacturer specifies a 3y warranty, then replace the drives every 2 years.