External USB HD shuts off after 10 to 30 min...

I’m running 11.2 and using a 1TB Maxtor OneTouch4Plus, P/N 9NT3A8-500,for all my mass storage. After about 10 to 30 minutes it powers off and won’t turn back on until I either unplug/replug or reboot.

That looks like a power management feature (issue), common to some models of Maxtor and Seagate drives.

Seagate releases workaround for linux users - The Inquirer

This thread describes how to disable power management with sdparm