When we need CAS in SCCM1012

I was working on  SCCM2012  design for a small environment and wanted to figure out if I need to incorporate CAS ( Central Administration Site ) in the design. Initially I was assuming that CAS will provide HA in the environment, but I was wrong . CAS is only required when we want to manage 100K+ clients  and when we have multiple primary sites. For a relatively small environment,  people are recommending to go with stand alone primary site.

Here are some links for a good reference on CAS:

http://social.technet.microsoft.com/Forums/en-US/d1daed7f-82d7-4f7c-8de2-9bfd81d74558/sccm-2012-cas?forum=configmanagerdeployment

http://mwesterink.wordpress.com/2012/12/11/sccm-2012-to-cas-or-not-to-cas-a-personal-opinion/

http://nuttyrat.blogspot.in/2012/07/planning-sccm-2012-migration-to-cas-or.html

http://msandbu.wordpress.com/2012/05/30/sccm-2012-cas/

http://sccmfaq.wordpress.com/2013/06/20/sccm-2012-to-cas-or-not-to-cas-that-is-the-question/