Editing Contribution batch takes ages and can cause a PHP timeout

Since 4.6.2 if you create a contribution batch fo say 50 records, and then save for later. If you try and edit the batch entries it now takes an inordinate amount of time for the entry screen to come up now. By default, you will get a PHP error "PHP Fatal error: Maximum execution time of 30 seconds exceeded" with anything more than about 5 records. I've extended by timeout to 360 in the PHP.ini file (max_execution_time = 360 ; Maximum execution time of each script, in seconds (I CHANGED THIS VALUE))

After reducing the number of transactions to 20 from 50, I can now edit the batch again after 1:20 sec.

You can easily duplicate this, by simply creating a batch, with 50 lines. Save for Later and try editing again.