Is there an automatic solution to extend the EOT Time for every single member at once (even though they all have different EOT dates)? Thank you!

Two Ways to Extend the EOT Time

s2Member stores the EOT Time in a user option field within WordPress. So the answer to your question would be yes. There are two ways to accomplish this.

1. Doing a Mass-Update with s2Member's Advanced Import/Export Functionality

Using s2Member's Advanced Import/Export Tools you can pull an export of existing users. Open the CSV export file. Edit the meta_key__wp_s2member_auto_eot_time data column. This data column will contain a UNIX Timestamp that you can modify using tools provided by CSV editors such as Excel, OpenOffice, or Numbers on a Mac. When you're done editing, use the modified CSV file; importing that back into WordPress with s2Member's Advanced Import tool.

2. Writing a Custom Script (MU Plugin)

This technique requires a bit of scripting. Here's a quick example.

Create this directory and file: /wp-content/mu-plugins/s2-extend-eot.php

add_action('init', function ()
       || $_GET['s2_extend_eot'] !== '[secret key]')
        return; // Nothing to do here.

    $days_to_add = 90; // Extend by 90 days.

    foreach(get_users() as $user)
        if(($eot_time = get_user_option('s2member_auto_eot_time', $user->ID)))
            update_user_option($user->ID, 's2member_auto_eot_time', $eot_time + ($days_to_add * DAY_IN_SECONDS));
    exit('All EOT Times updated.');

Now you can visit the following URL exactly one time to perform the update.[secret key]

Don't forget to replace [secret key] with a secret of your choosing. Also, you will want to change $days_to_add to the actual number of days that you want to add to each EOT Time.