archive
This depends more on the archive policy that you follow.
You can check the high water mark on the tables, the daily growth of the tables , space per block and then decide if it is the time to archive the system.
high water mark gives you the amount of space consumed, daily growth gives you the rate at which you are running out of space, and block size gives you the amount of space available.
considering these things you should be able to figure out the right time for archiving.