I have a 2017 SSD iMac and normally when I update to a new OS on past macs I have left the external time machine drive plugged in. Is it worth this year making a time machine back up, then turning time machine off, and ejecting the drive? Is it best with the APFS update to just have the iMac with no external connections or is this just something not to worry about. Just wanted some peoples views on best practices which may also help others as updating the file system is a bit different from normal years. Thanks in advance.