Hi,
think CU patching depends on company guideline/policy. We prefer to stay 1 CU behind. This page has a good list of CU for SFB: https://ucgeek.co/lync-updates/
Each CU also has information about new features and bug fixes.
One thing is for sure, don't install new CU on same day of release. This should ALWAYS be tested in lab environment first.
Please mark as helpful if you find my contribution useful or as an answer if it does answer your question. That will encourage me - and others - to take time out to help you. Thank you! Off2work