~80hrs on topic A squeezes the available time for being acquainted with the rest. [Edited because there was little way not to make the former formulation read, unwillingly, nasty]

Some of us believe instead on the advantage of being a polymath, (also) to be able to export wisdom from other contexts into the current work.

Also in terms of the proper ground to facilitate innovation.

Musk recommends 80-100hr weeks, every week

Source: https://www.youtube.com/watch?v=GtaxU6DZvLs&t=1m20s