Password expiration in CRM Online is indeed a nuisance and can be changed but the maximum password expiration period configurable using Office 365 administration portal is 2 years. If you intend to use O365/CRM Online for longer than 2 years, you may want to consider using Powershell tools to do it like a boss.

The following instructions are applicable to Windows 8 x64 machine and are abridged version of managing Azure AD using Windows PowerShell:

1. Install Microsoft Online Services Sign-In Assistant
2. Install Azure Active Directory Module for Windows PowerShell (64-bit version)
3. Start Windows Powershell and run the following script:

   Connect-MsolService
   
   Set-MsolUser -UserPrincipalName <user ID> `
      -PasswordNeverExpires $true
   
   # The following line will do it for all users.
   Get-MSOLUser | Set-MsolUser `
      -PasswordNeverExpires $true