pjmelect :
People forget that SSD drives lose their data when not powered up for a long time which makes them unsuitable for back up purposes. I think that I would prefer a large hard drive which would be cheaper as well. Backups should be done in the background when you are not using your computer so speed should not be an issue. I can't see why people would want one of these drives unless it is to transfer data from one place to another (sneakernet).
https://www.anandtech.com/show/9248/the-truth-about-ssd-data-retention
Your theory only applies to drives that are passed their endurance rating, 400 Terabytes of data written if we are talking about the 1 Terabyte 960 Pro.
"Remember that the figures presented here are for a drive that has already passed its endurance rating, so for new drives the data retention is considerably higher, typically over ten years for MLC NAND based SSDs"
The majority of people who would use the dual 960 Pro configuration would be for professional editing and rendering videos, likely in 4k or higher, that do not have access to a specialized NAS or SAN for their data needs, like Pixar/Lucasfilms would have.
http://www.slashfilm.com/cool-stuff-a-look-at-pixar-and-lucasfilms-renderfarms/
I wouldn't use this for backup, not because it wouldn't be reliable, but because it isn't cost efficient to use this device as a backup device.
For the $1800 that 1 - 2 Terabyte 960 Pro costs, I could get a 4 terabyte 860 Pro for $1700 and save $100 and get double the backup space.
Having said all that even I don't have an all flash backup solution for my house.
For backup for all computers in my house/streaming to any computer in the house/steam library, I use 6 - 10 terabyte Western Digital Gold in a raid 6 (zraid2) on a NAS4FREE server with 64 gigabytes of ram that also uses a 1 Terabyte Samsung 850 Pro as a read cache (L2ARC).
Hopefully with QLC an all flash array will be affordable.