InfiniteWP sends update notification with available updates at 10:00 (hardcoded time). To change this:

1. search in /iwp/controllers/appFunctions.php
2. for updatesNotificationMailLastSent
   or search for: 10:00:00
3. and replace the time

You need to change this after every InfiniteWP update.

Source: http://support.infinitewp.com/support/tickets/21249