Global Expiration Date
Short, concise description of the idea
A maximum age for all of the journal's entries. Entries any older go kaput.
Full description of the idea
The user sets an expiration date, of say four months and 20 days. Or, to make it easier in math, it could just be a number of days -- like 140, or 356+140=496. At some point, the server checks the user's oldest entry to see if it's older than the expiration date. If it is, the entry is truncated and dies forever. On to the now oldest entry for the same purpose. You could set this by default to something like 365 days, for all new accounts, and tuck it away somewhere. Maximum expiration date is a possibility. As an example of use, I would set my expiration date to like three months and just kick it freestyle from there. Why should I care what I said almost half a year ago? You could use your journal as an easy weekly planner; set the expiration to one week, or eight days for a buffer. Your journal could serve as a daily to-do list or memo-pad in itself; just set the expiration date to one day.
An ordered list of benefits
An ordered list of problems/issues involved
An organized list, or a few short paragraphs detailing suggestions for implementation
while (oldest_entry_is_expired = true)