This does not work for me. In cookie 4 everything worked nicely, just favourite the site and I was all set. With Cookie 5 only 1 of 6 sites keeps my cookies, in the others I have been saved over and over by Apples Keychain. I have favourited the sites, I have whitelisted all cookies, I have no idea what the "cookie timer" is, but logged out I am.
For instance www.boardgamegeek.com , I get logged out every time I quit Safari.