Set rules for dealing with duplicates

[so_la_la]

Hi,
only recently i discovered the duplicates handling possibilities. While i think this is a truly great feature i haven't got round to sorting out my duplicates (3000+ songs).
What I would like to do is to set up a rule which duplicate to keep/to display e.g. sth like: display only the file which is in the library for a longer time unless the newer file is bigger (or of a different file format etc.).
This would be handy especially when adding large numbers of songs to the library many of which presumably are already present in one form or another.