Trimming (or obsoleting) %changelog?

[drago01]

On Wed, Apr 17, 2013 at 5:18 AM, Mathieu Bridon
<bochecha at fedoraproject.org> wrote:
> On Wed, 2013-04-17 at 12:10 +0900, Florian Festi wrote:
>> For limiting the change log entries in the binary packages
>> %_changelog_trimtime can be used that take a unix time stamp as an
>> integer value. This way the whole history is still available in the spec
>> file.
>
> Could redhat-rpm-config set that automatically, for example to the
> release date of Fedora N-1?

Why does it have to be date based?
Why not having a count based cutoff?
Like last N entries.