I'd expect this preload script to remember the pages it's already fetched and not duplicate work unnecessarily. :/
If you really care about speed anyway, you should already have setup your site to max out caching opportunities (Etag, Last-modified, and replying "not-modified" to "if-modified-since" queries) - I'd suggest the author should ensure the script does support caching to the broadest extent possible - hitting your site whenever appropriate.
ps. I do tons of caching for any images and videos though. I know those things never change so have weeks of caching enabled.