If you want to disable password expiration on office 365 then please follow the steps as below.
Install the Windows Azure AD Module for Windows PowerShell from following link
Logon to office 365 from the proper powershell ( Windows Azure AD Module for Windows PowerShell) by following commands:
Use your Office 365 credentials
Run following two commands
connect-MSOLService -credential $cred
Get-MSOLUser | Set-MsolUser -PasswordNeverExpires $true
That will turn off password expiration for all of your accounts.