Pretty much what the others said, warnings should stay and shouldn't be cleared off from your history just because a year was overdue. It gives the Admins a good profile of someone, so they know what troublemaker they're dealing with.
Some warnings are warning which you've got when you started playing the game. I got some warning for things which I didn't know anything about, so those warnings give me a bad reputation..
Well it shouldn't be removed, but it should say that it has expired so to say, so that if there hasn't been another one in a long time, it seems like they've seen what they've done wrong, rather than to wipe the slate clean completely.
No... Just no. If you made mistakes in the beginning, you should show admins that you understand the rules perfectly well than ask for the warnings to be reset. Then again, this is just my opinion.