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

 

http://technet.microsoft.com/en-us/library/jj151815.aspx

Logon to office 365 from the proper powershell ( Windows Azure AD Module for Windows PowerShell) by following commands:

$cred=Get-Credential

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.

Type Exit