Some of the tech tree items take a lot of turns to complete. Some ships, especially the large ones with lots of advanced drives or weapons, are very very expensive. And some tile improvements can really take a long time to finish.
As my scientists, engineers, workers, and economists level up and as my civilization grows at the same time, I'm thinking that at some point, it makes sense to pull my highest ranked scientists and economists back to "Working For Government" so that they can benefit my whole civilization while I continue to train new scientists and economists on my research and manufacturing-focused worlds. Likewise with my economic and shipmaking centers in key locations throughout the galaxy.
And similar to that, when should I promote a scientist to shortcut an especially difficult tech tree item. Or promote a worker to complete a project, or an engineer to complete a ship?
At what point do things pay off for such a strategy?