Once you become a citizen, you have no reason to update your address with CIS. Having said that, I think it would be ok to update them anyway if you feel like it. It would be strange, since you are no longer their responsibility. They sometimes send erroneous post, but probably nothing you should worry about. I'm sure they have ways of getting in touch with you, like through the State Department's passport application list.
*** El Cafe ***
N400 - NYC (Brooklyn)
March 12 2010: Sent
April 7 2010: FP done- walk-in
August 3 2010: ID decision not made
December 12 2010: Lawsuit filed under 8 USC 1447(b)
March 31 2011: 31 Oath date
April 1 2011: Passport applied, picked up!