Office 365 does not have the ability online to have a password to never expire. The way to have a password to never expire is through PowerShell. After connecting to Azure in Powershell, type Set-Msol User -UserPrincipalName User ID -PasswordNeverExpires $true to make the password out one user never expire. If you want to set this for every user in the organization, use the command Get-msol user | Set-msol user -PasswordNeverExpires $true.