I'm curious what job you're describing where this is the case. It seems like one where extensive long term planning is common, and adaptability is not required

I'm curious what job you're describing where this is the case. It seems like one where extensive long term planning is common, and adaptability is not required. Everyone at my company who is good at their job would have their absence felt over the course of six months. For different positions, it would be different amounts of time, but I can't think of a single role from entry level to executive where someone could be so thoroughly good at their job that the company could ride along fine in their absence.