StatusExpire.php by tony baldwin | www.tonybaldwin.me released according to the Gnu Affero Public License, v. 3
Expires statusnet updates after a given period (here, 3 months, but you can edit that). You will have to edit the script to reflect your DBNAME, USERNAME, and PASSWORD, plus, of course, you can change the value in $oldate=date((Ymd), strtotime('-3 months')); from -3 months to whatever you like. Could be -10 days, -1 year, -6 months, whatever, and the script will delete updates older than that given value.
The statexpire.php is to be run from the command line with /usr/bin/php /path/to/statexpire.php not to be run in a browser. As such, it requires php-cli, but statusnet already requires that to run other scripts. I recommend sticking it in /statusnet/scripts/
You could have a cronjob do it:
0 0 1 * * /usr/bin/php /var/www/statusnet/scripts/statexpire.php
or some such thing.