Thanks for posting with your question!
Can you please say which dock you have? I’m guessing it may be the USB3-SATA-U3, however please let me know if I am mistaken.
A quick summary is and an update that improves sleep behavior for the USB3-SATA-U3 is here:
My short answer would be to update firmware if you’re very interested in sleep behavior of the dock, this way you don’t have to worry about manually turning it off.
Long story as short as I can make it is that the firmware currently on the dock is designed to allow Windows XP to work with larger volume disks, and sleep was a bit troublesome in this scenario. The firmware update enables “auto” sleep in conditions described in the post above.
Please let me know if you have any other questions!
MCITP Enterprise Support Technician