You receive free support and updates for 6 months after placing your order. If you ordered on 15 September 2015, you will receive major and minor update until 15 April 2015. If we release v5.1 on 15 October 2015 you would receive that update and security updates for that release would end on 15 May 2015. We only support a release for security updates for 6 months, then you’d need to update to a new version to continue receiving security updates.
Basically you are paying extra to extend your support and updates access to receive new major features. The access to the new versions would then extend the security updates as per our 6 months after each release date.
You’ll receive security updates for 6 months after every release, even if that falls outside your paid updates time frame. The security update would only be applied to the version thats included in your support / updates time frame (so it would just be a minor build update). Essentially any security updates that are issued wouldn’t give you access to any new version or major features.