When creating a new report under the Advanced pulldown there is an option to put in the user account you want the scheduled report to run as. It would be nice if this field had to option to use credentials defined under the Manage Windows Credentials in Settings. That would allow you to change the password used to run all the reports in a single place and eliminate the need to open each report to update the password.
Another bug in the process is currently you can set credentials manually and we use a system account that we know when the passwords get rotated on. By default if another user goes in and views your report the credentials get automatically changed over to that users account. Then when that person changes their password on AD it leaves the scheduled report with an incorrect password and the schedule fails.