That function will save only the first page, as multi-page EPS files aren't supported and there's no page range parameter in the saveAs() method.
It will save the EPS file, but it's subject to security restrictions on many levels - you can only run it in this mode as a batch/console script and the folder you're saving to must be allowed by the "safe path" rules. Run it in the JS console and you'll get an error if the path fails the sandbox test.
I will try a different tactic. Am I likely to have more success using Acrobat's Split Document feature?
You can use a loop that extracts each page of the original file, saves it as an EPS file (of course, you'll need to use a dynamic file name), and then closes it.