Actually, setting on graph creation might not be sufficient because that wouldn't account for old graphs from previous PromDash versions that need to be upgraded.

I've been wondering about this in general in https://github.com/prometheus/promdash/issues/112. Either we distribute these checks everywhere throughout the code in the components that use them (like this here), or we have a central piece of code walk through and update the entire JSON everytime a dashboard is loaded, and before any AngularJS magic starts.