RadRichTextBox is a complex control with many features and could be used in many different scenarios. There are many factors, which could affect the performance of the control. Depending on the scenario, the loading time could be up to 2 times faster. You could test the performance for your concrete scenario following the tips in this article
. Please, note that the improvements regarding the initial loading time of RadRichTextBox are available with Q2 2015 and you should have this or higher version in order to test them.
In addition, the galleries and the ribbon in RadRichTextBox are a big factor when it comes to initial loading time. You could remove them if they are not used in the application.
Hope this helps.
Do you want to have your say when we set our development plans? Do you want to know when a feature you care about is added or when a bug fixed? Explore the Telerik Feedback Portal
and vote to affect the priority of the items