No one ever "forgets" being hurt. Any future pain is a reminder to them how they were hurt once before. (Forgiveness doesn't mean forgotten).
Having said that more often than not when a person drags up the past it's because they are feeling as though they are losing the argument! Very much like politicians when running for office realize they're behind in the polls, suddenly they stop talking about the "issues" and look for "dirt" on their opponent. They want to put them on the defensive.
There are other times when a person may feel like they "let you off the hook" too easily without saying some things they later thought of. Therefore they use this opportunity to revisit the old issue in order to vent some more. Since you cannot control another person's thoughts or actions you are only left with how you choose to react.
Depending on how nasty the arguments are you may want to tell them, "Look I thought we had put that matter behind us but judging from the way you keep bringing it up maybe it would be best if we went our separate ways." Afterwards leave the house, go for a ride, see a movie, the mall or whatever to give them some time to think about what you said and the tactics they have been using.
Being given a "second chance" does not mean you have to take crap for the rest of your life from your spouse! No one is "stuck" with anyone.