what should be the best autovacuum configuration for daily partition table

I have a table with daily partition setup where old partitions are static tables that is after each day we don't get any new data in old partitions.

The database size is 2 TB and I am running with autovacuum on for Postgresql 8.4.

Now, I am facing a problem where old tables are not being vacuumed by autovacuum deamon and every now and then we are seeing autovacuum to prevent wrap around in the database and age(datfrozenzid) gets high for the database.

Any idea what should be best configuration for this type of database environment.

Thanks.