“Politicians, old buildings and prostitutes become respectable with age”

The movie Chinatown (1974), written by Robert Towne and directed by Roman Polanski, contained the following memorable line, spoken by the actor-director John Huston:
 
“‘Course I’m respectable. I’m old. Politicians, ugly buildings, and whores all get respectable if they last long enough.”
 
The line is sometimes given as “Politicians, old buildings and prostitutes become respectable with age” and falsely credited to the writer Mark Twain (1835-1910).
   
 
The Internet Movie Database
Memorable quotes for
Chinatown (1974)
Noah Cross: ‘Course I’m respectable. I’m old. Politicians, ugly buildings, and whores all get respectable if they last long enough.
   
13 November 1984, Chicago (IL) Tribune, “Hit hard by the wrecker’s ball” by Stevenson Swanson, pg. 15:
In its youth the building was probably thought rather plain, but like a politician or a prostitute it had become respectable with age.
   
Google Books
Chinatown ; The last detail : screenplays
By Robert Towne
New York, NY: Grove Press
1994
Pg. 80:
CROSS
(grunts, then)
‘Course I’m respectable. I’m old. Politicians, ugly buildings, and whores all get respectable if they last long enough. I’ll double whatever your fees are — and I’ll pay you ten thousand dollars if you can find Hollis’ girlfriend.
       
Google Books
The Complete Armchair Book of Baseball: An All-Star Lineup Celebrates America’s National Pastime
Edited by John Thorn
Galahad
1997
Pg. 83:
THOMAS BOSWELL
Mr. October
Mark Twain said that politicians, old buildings, and prostitutes become respectable with age. Reggie Jackson would like to make it a foursome.
 
Google News Archive
19 September 1997, Sonora (CA) Union-Democrat, Letters, pg. 6A, col. 2:
Mark Twain said politicians old buildings and prostitutes become respectable with age.
(Written by Ray Mellana—ed.)
 
11 April 2001, Dallas (TX) Morning News, “Texas chardonnays do the state proud” by Wayne Slater:
Kim McPherson of Cap*Rock paraphrased a line from the film Chinatown: “John Huston tells Jack Nicholson: ‘Prostitutes, buildings and politicians all gain respect with age,’” he said. “Maybe winemakers and wineries fall into that category.”
 
23 June 2008, Philadelphia (PA) Inquirer, “Karen Heller: City Council’s excellent vacation,” pg. B1:
As the old adage goes, “Politicians, old buildings and prostitutes become respectable with age.”
   
Crain’s Detroit Business
Originally Published: July 06, 2011 1:40 PM Modified: July 06, 2011 10:39 PM
The fantastical, farcical fictions of Kwame Kilpatrick
By Bill Shea
(...)
What’s the old saying? Politicians, like buildings and prostitutes, gain respect with age. So it’s not difficult to imagine Kilpatrick one day as the eminence grise of Detroit politics.