In my citizenship interview the officier mentionned that I should keep my landing paper forever. He said that when I retired one day, I would need my original copy in order to be able to collect social security. He said if you lose it you can order a new one, but he said that it took months to get a new one. So, I just thought I would share that so that no one would decide to throw it out after becoming a citizen, figuring you had no more need of it...