I don't sell clothing so this may not apply, and I may be teaching my granny to suck eggs, however:
If you bulk edit you can do bulk change in the 'condition' section for every category and sub category you list in. Click 'bulk edit' once you are in the bulk edit and it is one of the drop down options.
Or, in the bulk edit you can do an change to each listing. Do the bulk edit and then go along the headings and you should find 'condition'.
So, if the majority of your listings are 'excellent' bulk list to make every listing 'excellent' and then redo the bulk listing for the items that aren't 'excellent'. Not sure though if you can see what you have originally. I've never changed 'condition' but I've just done a bulk change in the description and if you across the headings to 'description' when bulk listing, and click, you can see the description for each listing. Still a pain but so very much easier than doing one listing at a time.
From experience, I wouldn't attempt to edit 1500 listings at once, sometimes it works but more often it doesn't - 200 at a time seems to work ok, but if you are going into each 'condition' 100 is even better - I know in the description if you mess it up and manage to fall out of the section - which I do frequently - the changes you have made individually are saved, so not too onerous.
Hope that makes sense, and I hope it works in your category.
