How long must a Hollywood film wait to use the same title of an older film?

According to this article I found (written in 2010) - individual movie titles can not be copyrighted. However, there can be a trademark granted if there is a certain level of recognition of the title to the specific movie. The author of the article cites "Star Wars" or "Citizen Kane".

Per the linked article, the MPAA has a Title Registration Bureau which also has a standard in place. Participants are notified of conflict; if a raised objection is not settled - the dispute moves to arbitration.

So - to answer your question - for the vast majority of film titles there is no mandatory waiting period. However, producers should not be shocked if there is litigation that arises regardless.

The answer is, they don't.

And I quote:

Literary titles – such as book or movie titles – fall in a gray area in U.S. law. For instance, although a book or movie is protected by copyright, its title isn’t. Copyright simply doesn’t cover titles.

And even if the title is distinctive, such as The 40-Year-Old Virgin, courts and the Trademark Office say it can’t be registered as a trademark, even though distinctive words and slogans can be registered as trademarks in other contexts. There’s an exception for series titles, such as Harry Potter, but that’s of no help to single-work titles.

http://www.slate.com/articles/arts/culturebox/2005/05/double_trouble.html

http://moviehole.net/201144916same-title-different-movies-stealing-another-movies-title

http://www.andsoitbeginsfilms.com/2013/07/top-15-movies-with-same-title.html

You might be interested in the case of the film The Butler which just came out recently.

The film's title was up for a possible rename due to a Motion Picture Association of America claim from Warner Bros., which had inherited from the defunct Lubin Company a now-lost 1916 silent short film with the same name.[9][31] The case was subsequently resolved with the MPAA granting the Weinstein Company permission to add Daniels' name in front of the title, under the condition that his name was "75% the size of The Butler".[32] On July 23, 2013, the distributor unveiled a revised poster, displaying the title as Lee Daniels' The Butler.[33]

http://en.wikipedia.org/wiki/The_Butler#Production

It seems to me there are often movies of the same title in the same year. IMDb keeps track of them with Roman numerals. Like this:

Action Figures (2011/I)
Action Figures (2011/II)

If there is a limit, it's no longer than three months. Two movies titled Nine came out in the second half of 2009. One is an all-CGI animated SF film with "stitchpunks" that look like a grown-up version of Sackboy from the later PS3 game LittleBigPlanet, released in September 2009. The other is an unrelated musical drama directed by Rob Marshall starring Daniel Day-Lewis, released three months later. Both are adaptations of previous works also titled Nine.