From: Alexandre Chapellon <alexandre.chapellon@mana.pf>

I have the very same behaviour here on my FR2.1.6 setup with PGSQL accoutning. It produce noisy logs but nothing unacceptable.
You can change this by not doing accouting for Stop Accounting packet that show up null session-time:

in your acccouting section:

if (Acct-Status-Type == Stop && Session-Time != 0) {
sql_accounting_module_name
}

Maybe relying on Session-Time is not a good idea. Try finding out another relevant attribute.

Cdt