Do NOT make a "new stuff" folder, or name a file "NEWEST".
It won't be the newest forever. It might not be the newest now! You never really know what's the newest.
You do know what the older or out of date items are. Once something is old, you know it's old, forever. Things that are old don't become new. You can safely label them old and not worry about your old label being out of date.
So label what's old because it's easy to label, then you'll be safe to assume that the items that are not old are new.
Labels that say "new" are not trustworthy. Don't use them.