Microsoft has released a hotfix to correct a .Net 4.5 issue in Windows 2008 R2 and 2012 & it applies to Exchange 2013 as well.
Since Exchange 2013 needs .Net 4.5, the Exchange Team has recommended that the hotfix be installed on all Exchange 2013 mailbox servers and multi-role servers.
At the time of writing, the hotfix needs to be requested from Microsoft and yes, it is free. Install the hotfix on all 2013 mailbox and multi-role servers and enable it by setting the registry key. Create a DWORD value at [HKLM\Software\Microsoft\.NETFramework\DisableRetStructPinning] registry subkey, and set the DWORD value to 1.
The hotfix will reduce the memory consumption in each store worker process. The server needs to be restarted after the hotfix installation.
Since the hotfix goes on mailbox servers, make sure that you do this in a maintenance window so that you can move around the databases, apply the fix and re-distribute the databases back.