No, LiveJournal does not delete old entries.
Your journal entries are kept forever unless you choose to delete
them. By default, only your 10 most recent journal entries are displayed on your main journal page, but you can change this
. You can also always access all your old journal entries from the Calendar
To lighten the load on LiveJournal's servers, you are only able to use the Recent Entries view to read up to 400 entries back. After this, you will automatically be directed to the Calendar