Yes, I have had the document open for half an hour or more--several times.
No, I did not copy it. I created it and edited it for a while (half hour or
so).
The funny thing is, that when I go to "File" \ "Properties" \ "Statistics"
the edit time is shown there and seems to be fairly accurate.
Also, I believe the edit time will remain the same if you copy the (closed)
document to a new folder on the hard disk. (Not sure what happens if you go
through floppy or CD. Haven't tested that yet.) However, if you do a "Save
As", the new file will be reset to zero, but the original will stay the
same.
P.S.
Luckily, I don't work for a boss who is concerned about edit time.
However, that edit time value does come in handy when billing customers for
work done.
Also it is helpful when trying to figure out where one might need more
discretion using one's time.