For those who would like to have loaded personal settings of DuckDuckGo in new session even though you are entering private mode or simply deleting flash cookies after quitting the browser, there is an easy solution of using the bookmarkler URL
set as default at your home page.
This works for every browser. (Safari, Mozzila FireFox, Google Chrome, Opera, Chromium, Gnu Iceweasel etc.)
Go to the settings page https://duckduckgo.com/settings
Configure your personal settings as you would like.
Once you are done with configuring your personal settings click on the "Show Bookmarklet and Settings Data"
Copy the "bookmarklet URL" inside of the box.
Step 5 Mozzila FireFox:
Go to "Preferences" -> "General" -> "Startup"
Set "When Firefox starts: Show my homepage" AND paste bookmarklet URL inside of the "Home Page" box.
Step 5 Google Chrome:
Go to chrome://settings/startup , you will see option add a new page, paste bookmarklet URL inside of the empty box and click ok!
Step 5 Opera:
Go to "Tools" -> "Preferences" -> "General" -> "Startup"
Set startup to show my homepage AND paste bookmarklet URL inside of the "Home Page" box.