I recently contacted WD to inquire about an upgrade I am undertaking: more specifically replacing my Green (and Blue) drive(s) in the main workstation with a single Red one. I specified the chipset and CPU, and made clear that this was going into a desktop computer that also served files for two other workstations besides itself (acting like a NAS). The WD support reply was (with apology for delay removed):
I'm good with it if WD are. Looking forward to making the upgrade, as my 6400AAKS has a Power-On Hour count of 24,706. That's some 1,029 days altogether, which comes in at just under three years of constant running. Never had single a problem with it, but I feel it's time to retire the ol' warhorse.[...]actually the WD Red is the best upgrade and it's specifically designed and tested for small office and home office.
(the 2 TB makes the most sense right now, I don't even have enough spare capacity to back up 3 TB of data)