In version 252 of systemd the os-release specification now includes a
new field SUPPORT_END which contains the date when the OS goes out of
support. [1]

In Cockpit we are considering showing a warning when the system is about
to reach end of support so it would be beneficial for us that Debian's
os-release file also includes SUPPORT_END. [2]

[1]
https://www.freedesktop.org/software/systemd/man/latest/os-release.html#SUPPORT_END=
[2] https://github.com/cockpit-project/cockpit/issues/20958

The proposed field would probably fit in a corporate world, where
there is only one vendor for the software.

But Debian is free software and there is not a single entity providing support.

Therefore, there is not a single value for the field which would make
everybody happy, and several people might have different views about
what date would be the right one.

So, no, for Debian I think it's much better that this information is
distributed elsewhere, not in /etc/os-release.

Thanks.