In Office 365 your password will expire every 90 days (unless your admin has changed the policy). If you are using Outlook Web App (or other online apps), you'll receive directions to change your password when it is about to expire or has expired. But if you are solely using the rich apps (e.g. Outlook 2010) you won’t get a notification. You might end up in a situation where your rich app fail to authenticate without indicating the true cause and you call support. This has changed with the upgraded Microsoft Office 365 Sign-In Assistant application (MOS SIA) downloadable from here.The new version of MOS SIA will give you a password expiry notification bubble from the Windows tray every day within the last 2 weeks before your password will expire. Clicking the notification bubble redirects to you to the Office 365 portal so you can reset your password.
Updates for MOS SIA are provided through Microsoft Update. Updates can be obtained directly from the Microsoft Update service or in managed environments through Windows Software Update Services (WSUS).