I have used ljarchive off and on, unfortunately, it is currently not working since Livejournal's latest changes have changed the code so much. So, no - sadly, ljarchive does not currently store an offline copy of the journal anymore.
Also, the Dreamwidth import seems to be broken for the same reasons. LJ did a thorough job :/
Must try ljbook. I am not eager to leave, but I like to save my stuff.