An interesting and informative website about Diego Garcia run by Ted Morris (a former USAF pilot) can be found at: The Provisional Peoples' Democratic Republic of Diego Garcia. It contains a wealth of useful information and photographs - some of it a little zany!
The 'window' for termination or renegotiation runs from December 2014 to December 2016.
President George W Bush arrives at Diego Garcia, 4 Sept 2007
Notice that the BritRep (the one with shorts in white) seems to be much smaller than the Americans - fewer hamburgers perhaps? And yes the Brit Navy seems to like making their officers look like schoolboys - hence the shorts.