Your green card may expire, but your status as a legal resident does not expire just because the physical Form I-551 [Alien registration receipt [green card] expires. If you have the means to simultaneously renew your green card [Form I-90] and file for citizenship [Form N-400] at the same time, I suggest you do both. You can never assume your citizenship application will be granted.
Answered on Feb 24th, 2014 at 8:30 PM