Try with Autotrash!
Autotrash is a simple Python script comes with Ubuntu 10.10 Maverick Meerkat which will purge files from your trash when they become older than a given days,purge older files to ensure a specific amount of disk space is free,etc.It uses the FreeDesktop.org Trash Info files included in the new GNOME system to find the correct files and the dates they where deleted.
- Remove files that are older then a given number of days
(autotrash -d N,where N is the number of days)
- Purge older files to ensure a specific amount of disk space is free
(autotrash --min-free=M,M is the amount of free space you want to ensure you have, in megabytes.)
- Check for remaining disk space, and only delete if you are running out
(autotrash --max-free=M,M is the amount of free space left, in megabytes.)
- Delete regex matching files first (see –delete-frist option)
For more info,execute this in terminal:
AutoTrash is already in Ubuntu 10.10′s repository,it can be installed from Ubuntu Software Center.For Ubuntu 10.04 and 9.10 user,install this from PPA:
sudo add-apt-repository ppa:nilarimogard/webupd8
sudo apt-get update
sudo apt-get install autotrash
For a different approach and a more comprehensive guide: http://helpdeskgeek.com/linux-tips/automatically-empty-the-trash-in-ubuntu/