CiviMail doesn't record email as delivered until the mailing finish

The CiviMail in 3.4.5 doesn't record email as delivered until the mailing finish.

In our case, we run civimail.cronjob.php every minute and sent a mailing to 2000+ recipients. If the cronjob runs exceed the max execution time, it will terminate and no delivered records inserted. If the cronjob runs again, the recipients who already got the emails before will get another one.

I noticed there is new function bulkCreate() are introduced which will need the mailing finish to bulk insert the delivered records. The delivered emails should be recorded during the mailing is running.

The current solution is to set the max execution time to a fairly large number.