I have observed that most of the people I know who fit your description: experts who work fewer hours but everything they do counts, almost always went through

I have observed that most of the people I know who fit your description: experts who work fewer hours but everything they do counts, almost always went through a period of ridiculous and obsessive long hours early in their career. Once you've built that skill set, it makes sense to dial things back because you now know how to be effective and you also probably do tons of mental work semi consciously away from your "desk." But it drives me crazy how people seem to think they can start out that way. In my experience that is a sure path to modest abilities, which is fine, but that's the trade off.