We'll that is true only if you have changed structural set ups and added items to Many pages. This would not be true if you went in and just changed how some of the elements look such as the size of an item, text fonts , colors, sizes and things like that. This is because most of those types of changes are only going to affect the CSS file.
TIP: copy your site to a safe location and test it out. Once you have safeguarded a good copy of your site, export your changes in RLM and only copy the CSS files to your working directory and see if all of your changes are there or not ( of course if you already know if they will or will not be there, then you don't need to do this test).
If you have only gone back to RLM to add a new page, then once again export your site from RLM and copy only the files that affect that page as well as the CSS pages.
So although if you make major changes to your pages you will most likely need to start over with replacing your content, that is not always the case and that makes adding new pages to a current site a pretty easy process too!
