I have been suffering from this for 10 months. Msft support was useless for this issue. It  affects Outlook as well.  (See Outlook losing connection to Exchange in Outlook forum. I got past the Outlook issues by using the web-ui version of outlook)

Lync has been constantly disconnecting and reconnecting. Every 5 to 8 minutes, all day, everyday.

If you have this issue and you use a D-Link router, this may be your solution!

Go to  superuser.com/.../why-does-my-d-link-router-keeps-dropping-my-outlook-and-lync-connection 

It really does seem to do the trick.

 The solution involves making D-Link router setting changes. It fixes the problem for me. A real relief.