Microsoft Online Service Portal (MOSP) doesn’t allow you to set passwords to never expires, but for some customers it is wanted and for some service accounts not beeing federated its also wanted.
Connect to Micorosoft Online Services.
$LiveCred = Get-Credential
Connect-MsolService -Credentials $LiveCred
Get-MsolUser BillieJean | Set-MsolUser -PasswordNeverExpires $true/$false