I've got a setting in my theme options panel to allow the user to switch the permalinks setting to support friendly URLs. I'm only allowing /%postname%/ and /%postname%.html as options.

I don't want to be triggering an htaccess rewrite everytime someone accesses a page on the site or views theme options, so I'm trying to code this to avoid that.

I've got an input field in theme options that's called $myTheme_permalinks. The default value for this is "/%postname%/" but the user can also change it to "/%postname%.html"

Here's the code at the top of theme options to handle this setting. Does this look sound?

if(get_option('myTheme_permalinks') =="/%postname%/" && get_option('permalink_structure') !== "/%postname%/" || !get_option('myTheme_permalinks'))
{
    require_once(ABSPATH . '/wp-admin/includes/misc.php');
    require_once(ABSPATH . '/wp-admin/includes/file.php');
    global $wp_rewrite;
    $wp_rewrite->set_permalink_structure('/%postname%/');
    $wp_rewrite->flush_rules();
    update_option('permalink_structure','/%postname%/');
    update_option('myTheme_permalinks','/%postname%/');
}
else if (get_option('myTheme_permalinks') =="/%postname%.html" && get_option('permalink_structure') !== "/%postname%.html" && )
{
    require_once(ABSPATH . '/wp-admin/includes/misc.php');
    require_once(ABSPATH . '/wp-admin/includes/file.php');
    global $wp_rewrite;
    $wp_rewrite->set_permalink_structure('/%postname%.html');
    $wp_rewrite->flush_rules();
    update_option('permalink_structure','/%postname%.html');
}