Well it could become admin-only at these times too

Or what I could also do is to limit by default to last x months, with a link to search in the older posts if needed (that feature was done in the next version of the site - I should take the idea in the current site)

Same for the list of all posts by the users, most of the time only the last ones are needed, but it still has to compute the full list for the list of page numbers.