Hi,

I asked this question 3 weeks ago and got no replies:

> * Sam Steingold <fqf@tah.bet> [2017-11-02 11:04:22 -0400]:
>
> Gnus has a few backward compatibility face declarations like this:
>
> (put 'gnus-group-news-4-face 'obsolete-face "22.1")
>
> Emacs 22.1 was released on 2007-06-02 -- over 10 years ago.
>
> What is the policy on removing such declarations?
>
> R releases?
> M major releases?
> Y years?
>
> Where is it officially documented?

To salivate our thinking, here are the obsolescence annotations in the
lisp sources (the code is attached):

--8<---------------cut here---------------start------------->8---
(insert-counter-alist
 (counter-table-to-sorted-alist
  (second (elof-count-all-obsolete "..../emacs/trunk/lisp"))))
                          25.1     193
                          22.1     172
                          24.3     127
                          24.1     125
                          24.4     123
                          23.1      88
                          26.1      65
                       Org 9.0      63
                          23.2      32
                       Org 9.1      15
                    Emacs 24.1       7
                          23.3       7
                          24.5       7
      Gnus 5.10.9 (Emacs 22.1)       6
                          23.4       5
                          22.2       5
                       ERC 5.1       4
                          27.1       4
                          21.1       4
        Gnus 5.10 (Emacs 22.1)       2
                    Emacs 22.1       2
                    Emacs 23.1       2
                       Org 8.2       2
                       Org 8.3       2
 speedbar 1.0pre3 (Emacs 23.1)       2
                     rst 1.0.0       2
                icalendar 0.19       1
                     CEDET 1.1       1
                    Emacs 26.1       1
                          20.3       1
         Gnus 5.9 (Emacs 22.1)       1
                         19.34       1
                    2011-08-02       1
    CC Mode 5.31.4, 2006-04-14       1
                at least 19.34       1
                  before 19.34       1
                          25.2       1
--8<---------------cut here---------------end--------------->8---

It does look like GNU Emacs 22.1 (2007-06-02) is a good cut-off candidate.