Save state keeps me from losing my work, I rarely use duplicate (and don't see how it would help anyways).
i didn't mean the exact command 'duplicate' prevents work loss.. just that 'duplicate' is a result (or requirement) of osx's autosave.
for osx autosave to work, it needs a place to save the data to.. if you're working on a new/unsaved document, the autosaves will occur on a temp file (at ~/Library/Autosave Information).. if you're working off a previously saved file, the autosave data is going to that file.
the key difference between the old way and the new way (as in, all the differing UI conventions are a result of this one thing) is.. you now name/save the file before working on it instead of waiting until you've finished the work to do those things.
you would use 'duplicate' if you plan on doing a 'save as' in previous conventions.. it's just that you do the 'save as' first instead of last.. (though for me, i don't use 'duplicate'.. i'll just option+drag drop a file prior to opening it which duplicates it.. you can also
right click-> Duplicate prior to opening the file.. doing it those ways, you don't have to open one then duplicate it then close it.
but even then, i barely duplicate a file in my workflow..i just let versions do its thing because i like having one main working file instead of 50 saveAs in a folder.. i'll sometimes duplicate when opening a large file in dropbox though..
anyway, aside from trying to adopt the new workflow, you still can do a 'save as' workflow in mavericks.. just work as you used to, when ready to do your 'save as', go File-> press&hold the option key.. 'Duplicate' will change to 'Save As'.. click that then in the save dialog, name it then uncheck 'Keep changes in original document' and save.. doing that leaves you with the original file untouched&closed with a newly named named file which has been save as'd.