Yes, the ones that I've obtained usually work for "a while", but that while is not up to my expectation. With most any other appliances, you can generally expect that it will last at least as long as the warranty period, but I've found that to rarely be the case with hard drives.
As far as the operating environment that my drives are subject to, I do not believe that it is abnormal in any way. The operating temperature of the drive in question is currently at 36 degrees C, and that is while it is in the middle of an error scan test being done by HD Tune, which warms it up a bit. I'm only doing that scan to determine if there is enough space left on the drive to be of any use for other purposes, because WDC's DLG has already failed the unit with too many bad sectors.
I didn't say that the warranty had changed, but that WDC's identification of the model of the drive had. I just got a response from them about the procedure to use to request a warranty review, but that is a lost cause, because I don't have the documentation that they require. As far as the length of time of the warranty, I don't know if it would have been any better with the right model ID, because when I first bought it their registration showed it with a shortened warranty time, which is how I became aware that I was sold old stock.
However, all that is now history and I'm trying to deal with the present, so I'm refocusing on my original question regarding the WD4001FAEX specifically.