Open a Windows PowerShell window with Administrative Rights.

PS > Add-PSSnapin Microsoft.Adfs.PowerShell

PS > Get-ADFSRelyingPartyTrust -Name:”relying_party“

PS > Set-ADFSRelyingPartyTrust -TargetName “your_relying_party_name” -TokenLifetime 7200

So this code set the session timeout as 12 Hours (7200 minutes )

Don’t forget to replace your_relying_party_name with the real name in your AD FS 2 Manager –>Relying Party Trusts

source: http://www.isvlabs.com/2011/11/how-to-set-dynamics-crm-2011-ifd-session-timeout/