|Leaving the external drive running continuously will expose it to whatever nasties might invade your primary drive. |
The only reason to leave connected is if you want your backup to be 100% current. That would still depend on the backup settings.
You can use other media to backup original work you create by saving to two places. Say the normal My Document/* and to say a flash drive, memory card, CDR, etc. I don't recommend flash or memory for long term storage. Just until you allow the external backup software to do its thing.
To add more comments. Losing personal files can happen for many reasons. Theft, fire, hardware/software failure, etc.
The more important the data the more care should be taken with it.
Your kids photos are not replaceable so you shoul maintain three or more copies. One or more offsite.
I burn those types of files to optical disk. Then you can make as many copies as you feel the need. I keep all my original disks of purchased software in a firesafe. I burn a copy when I first receive the disk and install the software using the copy. That way I know the disk is good and I preserve the original.
I also write the keys for software on the disk using a felt tip pen..