Here are 2 examples with Anno 2070 and Battlefield 3 with a rapid test, test temperature stabilized and the same test but with the latter two 120mm fans positioned around the map:
Anno 2070: 75 fps -> 63 fps -> 68 fps
Battlefield 3: 115 fps -> 107 fps -> 114 fps
The drop in performance once the temperature reaches cruising can be considerable. Efficient cooling can partially compensate for this decline, but there not a contradiction in having to add noise to compensate for a graphics card is trying to remain discreet at all costs?
It also raises the issue of reliability of performance comparisons that you can read here and there, since this may be the big difference depending on the test conditions (ventilation card but wait or not temperature rise of the GPU for measurements) between extreme cases the gain is 19% in Anno 2070 and 7.5% in Battlefield 3!
The frequencies that we obtained in practice for two selected scenarios: limited to 889 MHz map without additional cooling / card capable of up to 1006 MHz with additional cooling. 3DMark is only able to maintain the highest frequencies through the loading time between scenes that allow the GPU never have time to reach 80 ° C.
3DMark Fire Strike: 889/1006 MHz
Unigne Heaven 4.0: 876/954 MHz
Unigne Valley 1.0: 876/954 MHz
1920 Alan Wake Max: 876/993 MHz
Alan Wake 2560 Very High: 837/928 MHz
2560 Alan Wake Max: 876/954 MHz
Anno 2070: 837/902 MHz
Assassin's Creed MSAA4x March 1920: 876/967 MHz
Assassin's Creed March 2560 FXAA HQ: 850/941 MHz
Assassin's Creed MSAA4x March 2560: 850/928 MHz
Batman Arkham City AA8x: 876/993 MHz
Batman Arkham City 2560 AA4x: 876/954 MHz
Battlefield March 1920 MSAA 4x: 876/993 MHz
Battlefield 3 2560: 850/928 MHz
Battlefield March 2560 MSAA 4x: 876/954 MHz
Civilization V AA8x 1920: 850/928 MHz
Civilization V AA4x 2560: 837/902 MHz
Civilization V AA8x 2560: 863/954 MHz
February 1920 Crysis Ultra: 876/993 MHz
February 2560 Crysis Extreme: 876/954 MHz
February 2560 Crysis Ultra: 863/967 MHz
DiRT Showdown 1920 Ultra: 876/954 MHz
DiRT Showdown 2560 Ultra AL OFF: 837/928 MHz
DiRT Showdown 2560 Ultra: 863/941 MHz
Far Cry AA4x March 1920: 876/954 MHz
Far Cry 3 2560: 850/928 MHz
Hitman Absolution: 876/993 MHz
Max Payne 3 4x AA: 876/954 MHz
Max Payne March 2560 NOAA: 850/941 MHz
Sleeping Dogs: 837/902 MHz
The Witcher 2 Enhanced Edition: 876/954 MHz
Total War Shogun MSAA4x February 1920: 837/928 MHz
Total War Shogun February 2560 MLAA: 837/928 MHz
Total War Shogun February 2560 MSAA 4x: 837/901 MHz