It’s not nevessary to unmount the drive after you have finished recording. Just make sure that the device has finished writing to the disk before unplugging – so wait until the record button stops blinking.
Is it realy possible to removal of the USB Driver without any preparation? At least such a “hot shutdown” will not affect the performance of the HDD? in fact, the HDD light is on constantly, it is mean what that was in progress and suplaying