What is the use of "Backup set will Expire:" option while creating Backup Database task in Maintenance plan While backing up the database, I would like to use "Backup set will Expire:" option to delete/overwrite old database backups. I am not able to use this option.

Any advice on how to use "Backup set will Expire:" options while creating Maintenance plan will be appreciated.
The "Backup set will Expire" option is used to indicate how long a backup should be prohibited from being over written. It will not clean up old backup files. You can use the "Maintenance Clean up Task" in your maintenance plan to clean up backup files older than a certain number of days.