4-6 days, it's unreasonable to extend it any farther than 1 or 2 cities.
i could easily spend 6 days in just LA.
getty is a full day. LA Museum of natural history is a full day. Griffith Park is a few hours. La Brea tarpits is a few hours. walking around venice boardwalk is a couple hours, santa monica pier is an hour or 2... get dinner at swingers....
I just realized I read that wrong. you meant 4-6 days in 1 location, i guess.