Ran into some stability issues with a Lync 2013 environment recently with calls being dropped and content sharing not working. Restarting the Edge Servers, and less commonly the Front End servers, resolved the issue but only for a few days at most.
Working with MS support they identified high namespace handle count against an svchost.exe process – the process that was associated with WMI. To identify this, WMI was broken out into it’s own svchost process using the information in the following article: http://blogs.technet.com/b/askperf/archive/2014/08/12/wmi-how-to-troubleshoot-high-cpu-usage-by-wmi-components.aspx
Once the cause was identified, the following hotfix resolved the stability issues: https://support.microsoft.com/en-in/kb/2889748/en-us