I'm not sure exactly what you're saying -- are you saying that you think consumer drives might be expected to die faster than the backblaze drives, or?
They use consumer drives in a climate controlled environment - their usage scenario is completely different from a normal consumer.
Theirs are constantly spinning 24/7, as they mention - a normal consumer turns off their computer when they're finished, they turn it on when they want to use it.
Power on/off causes components to expand and contract, (resistors, PCBs, etc), as they start at close to ambient temperature and heat up as time goes on. This movement while extremely small can be enough to stress either the solder joints or the components themselves - something a constantly on device isn't subjected to.
You also have Inrush currentw
when a device is turned on - if you look at the manufacturers data for HDDs, Startup current is higher than what's required to keep it spinning - this current, while used predominantly by the motor and its associated components, could possibly affect other components that aren't rated to keep handling such transient surges.
Evening things out though is the comparison of the time BackBlazes HDDs spend spinning, (24/7), and the time a normal consumers HDD is spinning, (eg. 6-18 hours per day, 5-7 days per week, etc).
All I'm saying is that until someone does a comparable study of consumer drives and how they're generally meant to be used then saying they may or may not last longer is a bit pointless.
The only thing you can say about a HDD, (and any storage device), is that it will fail at some point ... and that's what you plan for.