We have tested leaving the XU1541, XUM1541, ZoomFloppy, XA1541 or XM1541 adapters connected to powered-on drives for days with no problems, even though they were not connected via USB or via the PC's parallel port. You can also leave the adapters plugged into USB with the drive(s) off with no problems. But while the ZoomFloppy is designed to be robust, you can avoid unnecessary wear by following these instructions for starting up and shutting it down. Other adapters (XU1541, other XUM1541 variants, XA1541 or XM1541) may be even more picky than the ZoomFloppy.
For USB based adapters (XU1541, XUM1541, ZoomFloppy), the following procedure is recommended:
Turn off the equipment via the same sequence in reverse, at least doing steps 4 and 3. You don't need to unplug the floppy drive from XU1541, XUM1541 or ZoomFloppy while not in use.
The 15x1 drives with an internal power supply tend to get hot if left on for a long time, so you may want to power them off when not in use.
For the parallel port based adapters (XA1541, XM1541, XAP1541, XMP1541), the following procedure is recommended:
Turn off the equipment via the same sequence in reverse, at least doing steps 5, 4 and 3. It is highly suggested to unplug the floppy drive(s) from the parallel port while not in use, by removing the XA1541, XM1541, XAP1541 or XMP1541 adapter from the PC, at least.
The 15x1 drives with an internal power supply tend to get hot if left on for a long time, so you may want to power them off when not in use.