FWIW, my perspective on this is more that we should take it as an act of periodic maintenance that all forms of little, mindless busywork should be eliminated from the group's rituals and routines. If it's not necessary, don't do it, and to quote Sutter: don't sweat the small stuff. The problem being that this stuff accumulates over time and weighs everything down, it creates cobwebs that eventually have a risk of becoming too annoying to eliminate, in a vicious loop.
I have proposed before to move to a system based on SPDX before for the same reason, it reduces busywork that brings no advantage. And as it's been suggested before in the thread, the bulk advantage of accurate/updated copyright years is likely to be somewhere between small and modest, to be generous. Like Han-Wen, my own perspective was also informed by many discussions had at various employers and with various other houses and bodies investing big money in software in a variety of ways. Disclaimer: Whatever I say here shall not be taken as me representing the opinions, views or will of any of them and I am not a lawyer L -- Luca Fascione