Unfortunately Brave has been following the Chromium model and it only keeps History for 90 days. If there are any particular sites you’d like to not forget, you may want to add to bookmarks or you can perhaps try to use extensions such as History Trends Unlimited which people have sworn by for years.
And to show you the official response to similar questions, so you know I’m not making it up on the Chromium aspect:
And then Mattches went to Github to request as part of something else that they add the ability to save longer, but there’s been no movement on it since he added that in February.