How to check nonce lifetime value of plugins?

Check codex info about Nonces life time here.

Here is a quick code that will echo life time of nonces in footer of your site’s front-end as html comment. Put it in your functions.php file.

$n  = "";
add_filter('nonce_life', 'wptuts_change_nonce_hourly');
function wptuts_change_nonce_hourly( $nonce_life ) {
    global $n ;
    $n = $nonce_life;
    return $nonce_life;
}

// Display in footer comments
add_filter("wp_footer","d");
function d(){
    global $n;
    echo "<!- Nonce Life =". $n ."-->";
}

NOTE: This code does not give the ideal way to check life time of nonce, but a quick fix to get the desired info. You should delete this code from functions.php once you get the info.