[HamletEagle]

You should have a deletion option along with archiving. There is no reason to keep troll/insulting messages or messages that are like 6 months/1 year old. Or the message could simply be useless and you don't want the archive to become messy/filled with garbage and make it harder to search for a specific message in the future. You may want to keep in the archive only messages that may be needed at a later date.
And at the end of the day, this gives more power to the end user, which should always be welcome.