pekak, I just quoted Newtziv because I knew the story to illustrate his personal view of vacations. I don’t know how other roshei yeshivos spend their free time, never met one at a beach … I do understand that many people need time to recharge, and there are psakim to that, just trying to keep in mind what the ideal is.
As to high-intensity jobs, I think, many of such people, including myself, should consider reducing their hours and spending them learning themselves and with their family. It is very alluring to use your expertise on the job when you are a baki ( as Resh Lakish responded to R Yohanan’s comment about sword making – “I was called Rabbi there and I am called Rabbi here”), but Torah and education (and they personally) will probably benefit if people with proven thinking and organizational abilities contribute more. As R Twersky writes “none of the older patients ever said – I did not spend enough time in the office” and in another place – a kid suggest paying his father psychiatrist his hourly rate to spend time with the kid.