response inline; in general, I don't bother with low usage/high time requirement features and leave it up to the community to research (and even implement) what they want the program to handle.
if you make any changes to the save file (ie set anything) without exporting the save, you'll get an alert. I don't see it necessary for checking even further back if the pkm that was loaded was modified (if nothing else has been set yet). I mean, I can always set the "Edited" flag when something has been viewed, but that could end up nagging people who quickly opened to view something.