The graph IS serialized only when a change is made, except for one occasion, and that is when the graph asset is selected and thus it’s inspector is drawing.
That might sound weird, but the reason behind this, is that Unity force calls the ‘OnBeforeSerialize’ method in every editor frame update when an object’s inspector is shown.
If you deselect the graph (or simply select something else for example), you will notice that the graph will no longer serialize every frame and you will not any longer encounter these performance hits.
Gavalakis
