Here is a recent email conversation between me and Western Digital Customer Support:
Dear Sir. I note from the product specification page on your website for this hard drive, that the safe operating temperature is stated as a maximum of 60' centigrade. I would like to ask if it is safe to run this hard drive at an operating temperature of 50' (fifty degrees) centigrade for 14 hours a day, 365 days a year, or whether prolonged operation at this temperature would reduce the life of the device? I look forward to your reply, and am grateful for your assistance. Regards, Pipps.
And here is the reply which I received:
Thank you for contacting Western Digital Customer Service and Support. My name is Hector A.
Working in the range of the operating temperatures will never harm the hard drive, however as with any other electronic device there is a direct relationship with the use of the device and its lifecycle, the most you use the device shorter will be its life. Always make sure that the room in which you are using the PC is well ventilated and always check that the fans that you may have installed internally in the PC case are working properly.
If you have any further questions, please reply to this email and we will be happy to assist you further.
Western Digital Service and Support
I suppose these comments suggest that WD are perfectly comfortable with customers using their hard drives at 50'C.
Though whether there comfort is derived from confidence in their device's abilities, or the thought that I would consequently need to buy a replacement hard driver sooner rather than later, is open for debate!