Bug 20961 has been fixed, but it should also be possible to set per-page how old the last included thread should be (e.g., 7 days). It makes sense that on some pages you show all recent discussions, even if they're many, because they all need the same attention (e.g. [[WP:AN/I]] and similar pages or the village pump), espcially if you can't mark a thread as closed/resolved (see also bug 24815).
Version: unspecified
Severity: enhancement