Use a filter in your themes functions.php (- and remember to use child themes!)
add_filter( 'wcl_password_expires', function(){ return time() + [lifetime_in_seconds]; });
Where your lifetime_in_seconds is 30 * 24 * 60 * 60 (days, hours, min, seconds) = 2592000 – so it becomes:
add_filter( 'wcl_password_expires', function(){ return time() + 2592000; });
