I use a backup facility (daily) to backup my mail - called Winmail Backup 2. This file can be restored back to a Winmail system within any user profile. What I have done is to backup the full system at a given point in time e.g. end of period/year.
1st Method - not ideal but manageable
Set up another USER on the PC and restore this file to Windows Live Mail (set for off-line use only). Subsequent archives - use 2nd Method below but restoring within this user profile or another user profile, etc
2nd Method - Messy
Restore the file to a specific folder within your user profile and 'swop' to this folder within Windows Live Mail (Maintenance tag) for when you want to refer to archived messsages (don't forget to switch to off-line usage first as new messages will keep arriving. Swop back whne finished.
Whichever method is used, you will still need to manually purge mail from folders, which being under your control can be by folder, by date, by user, etc.