Custom Excerpts Per Page

by

Here’s a solution that should do what you want (per your questions in comments and chat):

Functions.php

function wpse102641_custom_excerpt_length( $length ) 
{
    // assuming your category is called "Stories"
    if ( is_category(  'Stories' ) ) {
       return 50;
    }

    // return default length
    return $length;
}
add_filter( 'excerpt_length', 'wpse102641_custom_excerpt_length', 999 );

References

Codex: