excerpt configuration on archives pages

To modify that you would have to edit core files which is not a good thing. Better try this plugin:
https://guff.szub.net/2005/02/26/the-excerpt-reloaded/

Moshu–

Thanks for the information. I looked at the plugin but decided it was going to do what I could accomplish with existing tools. This is what I did:
1) I realized that if I created my own excerpt, the […] no longer appeared, so that eliminated one of my problems.
2) In playing around the with the excerpts, I determined that ending the excerpt in the middle of a phrase makes it more obvious that it’s an incomplete post, and I also added … so that it was clear that there was more to read.
2) In archive.php, I added this code to beginning of the postmetadata display (the php and link I simply copied from what surrounds the post title):
<p class="postmetadata">" rel="bookmark" title="Permanent Link to <?php the_title(); ?>">read the entire post » | Posted in ...
This puts the link right before the categories; this way, the read more link doesn’t add another line to the entry.

One more note: creating my own excerpts means that my excerpts can be formatted; the default excerpt strips all code, and so linebreaks and other formatting is lost. This means the excerpts look better too.