check your advanced power settings and make sure USB selective suspend is turned off if it really bothers you. Also PCI express link state management if you have a raid and/or extra SATA card installed.
I still let my hard disks turn off after 20 minutes of non-use. Obviously, my main *whore* drive almost never turns off because I usually have some kind of torrent running.
Just broke my personal record for number of consecutive days without dying!