Depends how you want to shorten it. See
Preferences ==> Saving books to disk
I prefer the following template, modified from the original:
Code:
{author_sort:list_item(0,&)}/{title}/{title} - {authors:list_item(0,&)}
Which merely switches the authors fields to use the list_item function to restrict a many-authored book (anthologies) to only using the first author's name in the filename.