The new RadEditor for SharePoint 2010 has a feature, which can improve load times on pages with two or more active editors of the same type. For example, if you have a publishing layout with more than one content field and all HTML content fields have the same configuration. Another example of many editors is a list with two or more fields of type "Multiple lines of text".
If you want to take advantage of the shared toolbar feature, you simply need to set the UseSharedToolbar editor property to True in the configuration file (see Set Properties Via Config File):
After you set the property to true, the editor will automatically check if there are multiple instances of the same type when loading a page and will optimize the HTML output. Note that using a shared toolbar means that all editors of a particular type (e.g. all publishing fields) will have the same configuration (same tools file and same configuration file). This should lead to an improvement in HTML size of about 5-7 KB for each editor instance after the first one.
If you want to further improve the loading time of the page, make sure that the editor toolbar mode is not Default - i.e. use ShowOnFocus or PageTop:
This way each editor's toolbar will be initialized only after you click in its content area and not when the page loads.