You usually have to qualify for it each calendar year, but sometimes like this year, United is ectending it if you pay $25 till March. In most cases, you have your status through February of the following year.
So if you qualify in 2002 you will have status for all of 2003 and January and February of 2004. To continue that status you have to qualify again in 2003.
Million miler status is different, if you were near that you wouldn't be asking.