For the index.php (home, search etc pages), within the “WordPress Loop” the I check for the MAX_SUMMARIES_PER_PAGE for displaying the excerpt of the topic. If the counter is greater than the above constant, then till the number of topics per page (which can be set in “Options”) the I display only title and meta information.
As far as the implementation of the “long-tail” archive, I frame the query to wp_posts table myself with LIMIT offset, number-of-archive-topics-per-page. Just take a look at the “archive.php”.
For the “category” and “date” -wise archive, I handle them in “archive.php” itself using the “$wp_query” object.