Sometimes we may have the need to change the time-out period for our OWA sessions while using O365.
O365 supports 15 minutes (00:15:00) at its lowest setting, up to 8 hours (08:00:00), with the default being 6 hours.
Set-OrganizationConfig -ActivityBasedAuthenticationTimeoutEnabled $true -ActivityBasedAuthenticationTimeoutInterval 00:15:00 -ActivityBasedAuthenticationTimeoutWithSingleSignOnEnabled $true
Disabling the time-out period for Office 365 is currently not supported.