Domained Win2k3 servers using scheduled tasks. Tasks can be created when logged on server as myself or as "service account" ID. Both are domain admins, builtin Administrators and Backup Operators via Active Directory.
The "run as" user is set to the service account which does not have an expiring password. The "run only if logged on" is not checked.
These tasks will run fine for a while. I'll remote in to a server took do checks, see a job that had failed with Status of "Could not Start". Open up the task and see that the user is now set to my userID.
My assumption is that during a previous logon to that server, the scheduled task changed the "run as" account on that task. This is random and hits random tasks at random times. I have about 15 task on each of our remote servers that run throughout the month. Each is set to run as this service account. Most are created by group policy, some are just copied in from a *.job file.
For manually created jobs, what I do is: I log in to the server as the "service account", create the task to run as the service account, copy that job to a network share, copy again to another server, log on to that server as the service account, edit the job properties and confirm the service account is still set as "run as". But then weeks to months later, I'll check back in (as my userID) and see that the task failed to run as some point. I'll edit the task and see that the "run as" has changed to my personal userID.
I then have to go through all the servers then again, check for failed tasks and change the user name back to the service account. Changing the "Run as" back to service account forces me to re-enter the correct password.
Again, password does not expire.