I am not using MySQL that much, but I've written an extended Zend_Db_Adapter for Oracle covering my needs.

I think you could have written an adapter which looks something like this :
[geshi lang=php]
class My_Db_Adapter_Oracle extends Zend_Db_Adapter_Mysqli
{
protected function _connect()
{
parent::_connect();

if (!mysqli_ping($this->_connection)) {
$this->closeConnection();
parent::_connect();
}
}
}
[/geshi]
It's smarter and should only disconnect/reconnect when a problem occurs.

As the proposed solution is no much than implement a non persistent connection to MySQL (and I think could be achieved by a mysqli configuration).