Describe the new feature or change to an existing feature you'd like to see

Understand AMP is an ongoing project and is aimed to provide more and richer components/ features to the users but as the development moving on, it is unavoidable that some of the components that are working fine now, will not be working in future with the latest version released.

As AMP Community is getting bigger and components are more mature (lesser bugs), we are hoping to have some version controlling mechanism, such as if the developer is comfortable with a particular version, the developers may have the option not to UPGRADE until there are new features which may be helpful and attract the developers to do so.

Describe alternatives you've considered

Two approaches which I can think of

1. If AMP Team is concerning about large numbers of versions are difficult to be maintained, may set the release lifespan a little bit longer, such as a stable version every 3 months, and developers may do a Full Cycle Test every 3 months before adopting the new version, and any Stable version will only be maintained for a certain period, and be replaced by any newer version.
2. Token Mechanism, <meta name="amp-experiment-token" , not too sure how this works but sound this meta tag can determine current domain which binds to a certain version of JS script for specific feature

Thoughts ？

/to: @aghassemi @choumx