best way to run maintenance script

Hi all,
  I have been searching for the best way to run maintenance scripts
which does a vacuum, analyze and deletes some old data. Whenever the
maintenance script runs - mainly the pg_maintenance --analyze script -
it slows down postgresql inserts and I want to avoid that. The system is
under constant load and I am not interested in the time taken to vacuum.
Is there a utility or mechanism in postgresql which helps in reducing
priority of maintenance queries?

Is writing a postgresql C function and setting the priority of process
the only way to change the priority of the maintenance script or is
there a better way.
http://weblog.bignerdranch.com/?p=11

I tried using the nice command (Linux system) on the maintenance script
- it did not have any effect - guess it does not change the niceness of
the postgresql vacuum process.

(I am running Postgresql 8.0 on a Linux)

--
Vinu