B.W.
Graco expires 6yrs from the date of manufacture, in the December of the year of expiration. So if it was manufactured in 2005, it will expire December 2011. Check the date stamp or the sticker for the date of manufacture.
My boys are 3.5yrs apart and I used the same infant seat for my second that we used for our oldest. As long as its not expired, its not been mistreated, not been in an accident, the harenss hasn't been washed and its been stored safely, its good to use.