As the system logs into the Administrator account, the Pass 7 sync commands will run. The disable-password solution used here should disable the password timeout for the account. If you run the command manually after setup is complete, does the command work?
I don't use this password expiration solution when I build an image. Instead, I create a custom security policy and have the policy imported with a Pass 7 sync commands. It works every time:
Secedit.exe /configure /db temp.sdb /cfg c:\setup\mysecurity.inf
mysecurity.inf is the custom security that gets created with MMC snap in.