I work for Buffalo, and would add the additional information.
First, to the post above that mentions the three year warranty, please understand that 3 year warranties are for the TeraStation class products; LinkStation class products feature a one year warranty. Both LinkStation and TeraStation have the BitTorrent download feature.
All Buffalo NAS devices are designed to run 24/7. ?As far as BitTorrent in general. BitTorrent as a protocol writes data in very small chunks and if it is running 24/7 will be writing (and reading) more actively than a traditional user. There is no scientific proof either way about how this affects hard drives. Many hard drives have premature failures without much disk activity, and many drives last forever in high disk load states. Google has done some analysis on SATA hard drive life expectency. The electronics themselves (the LinkStation parts without the hard drive) will not have any additional wear or concern.
There are studies that link hard drive life expectency with heat. Buffalo monitors the heat of various components and uses fans to cool drives. Users can take additional measures to lower heat by ensuring the NAS device is in a well ventilated area away from other heat-generating sources. TeraStation class products have larger cooling systems.
I'm sorry there is no conclusive answer to this, but it is something that would affect any consumer/small business device with BitTorrent.?
As mentioned, it's always important to backup any data you can't afford to lose (or don't wish to lose). Should hard drives fail, they can be replaced (in warranty for free, or out of warranty at your expense).