I believe warning letters now stay for 36 months. In addition to 3 in 12 it is now also 5 in 36.
I am aware of an employee who was just terminated under circumstances that are truly shocking. If what the employee is saying is true, he probably has a case that could be worth an enormous amount of money. I don't want to tip FedEx, so I won't go into particulars, but suffice it to say that this could make the news as a story of corporate cruelty and gross mis-application of policy.
I think most of us here have seen FedEx in-action when they want someone gone, and then equal application of policy goes out the window. They use it (especially 2-5) however they wish, which flies directly in the face of how policy is supposed to work. If your head is firmly up management's ass, kissing as hard as you can, some way will be found for you to evade application of the rules. But, if you question authority and application of policy, they will herd you at the door as quickly as possible. Sorry, but that's not the way it works, and this is why FedEx ends up in court as often as they do.