If you work for the post office, you're a civil servant. The Civil Rights movement focused on the notion that all American citizens were entitled to the same basic civil liberties.
There is also time limit to consider for sending the amended returns, and it is generally three years from the time you filed the returns or two years after the tax payment (whichever is later). If you plan to amend more than one tax return, you have to file separate 1040X for every one you want to change.
It depends on how accurate your return was, what records you are talking about, etc. It's anywhere from 3 years, to 6 years, to forever. 6 years might be a good idea, especially for collection reasons. In many cases, the IRS will require the last 6 years of returns before working with taxpayers. If the IRS lost your return, you might need to resubmit it--so maybe 6 years generally, and 10 years or longer if you think the return might be incredibly weird.