Status is from the day you earn it until all of the following

• The remainder of the year you earn it
• the entire year following the year you earn it
• January and February (and maybe March, not sure) of the year after that

So anybody who earns Status anytime in 2010, be it January 2 or December 31, will have that status until March of 2012

Status has to be earned every year, on January 1 your status count resets to zero and you need to meet the requirements.

Because of the way Hilton does it, it's is possible to maintain status by not staying with them at all in a given year, if you can requalify in January and February of the following year if you want to concentrate on another program, before your current status expires.