AUDIT ALL BY <user>

I am looking to enable auding on my 10g(soon to be converted to 11gr2)
system and have a few questions.

Ie AUDIT ALL by

I am going to set audit_trail=xml, which means that files will be created on
the file system. I know the default location of audit files is $ORACLE_HOME/rdbms/aduit to over-ride that location I can I set audit_file_dest=''

Secondly, does Oracle provide a tool or cleanup process for the .xml
files that will be generated or is this something I need to create a script for?

Ie; when using adrci I know I can use the purge command to remove
incidents, cores, ..... does Oracle have something like this for removal
of audit files.

As far as I know there is not automatic purging on audit records - not even for AUD$ table therefore I would plan on doing it via a custom script.