From the Adobe Blog:
A Creative Cloud subscription offers numerous benefits, including frequent product updates with new features and capabilities, critical bug fixes and important security updates. We recommend all customers use the latest release of Creative Cloud for optimal performance and benefits.
Please note that going forward, Creative Cloud customers will only have direct download access (from the Creative Cloud Desktop app and Adobe.com) to the two most recent major versions of Creative Cloud desktop applications.*
Focusing our efforts on the latest two major releases of Creative Cloud applications, which the vast majority of Adobe customers are already using, will further enable us to develop the features and functionality most requested by customers and ensure peak performance and benefits across Windows and Mac operating systems. Business customers in need of an older version of a Creative Cloud application should contact their IT Administrator to see if one is available.
*Exception: Only the most recent version of Adobe Acrobat is available for download.