Frankly I don't see much purpose in having an archive of all the weekly messages, which is why I've never done it. They don't contain lasting information that we'll need to reference later on. Its info for that week only, anything that needs attention beyond that week is included in the following weeks' messages. I can't recall any instance that we needed to check an earlier week.
Even the promotions are not a big deal. You know if you got a promotion because you know how many commendations you've earned and can see if your fleet rank changed.