WebSite-Watcher always saves the last two versions of a web page, it's not possible to keep more than two versions.
If you want to archive pages permanently, you can do this with the software Local Website Archive.
You can add pages from WebSite-Watcher to Local Website Archive manually or automatically with each detected update. More information can be found at https://www.aignes.com/wswhelp/help_using_local_website_archive.htm
Local Website Archive is an add-on that must be installed separately. You can download it from https://www.aignes.com/lwa.htm