30 Minutes To build.... How long does yours take?

Building just twice is enough to know if it makes any difference. The major benefit from caching is more to do with asset import / conversion, so it might not make much difference if the only changes are to your scenes.

We'd have to know what's in your scenes to have any idea of what's making them take so long. Could it be that there's stuff duplicated between them that can't be reused for some reason or other? (Ie: it's built into the scenes rather than being separate assets?) For what it's worth, I've a large, relatively complicated 3D game with ~70 scenes which on my laptop (7th gen i7 and a mid-range SSD) takes ~10 minutes to build.

 

More than 1h. Not a first build.

 

At this rate it should be finished in a week or two.