You could have your clients update from the Current branch and do your testing using the Evaluation branch. You could have ePO download DATs to the Evaluation branch, and set the download schedule to every other day (Weekly, Mon Wed Fri) or however often you want. When you are satisfied with whatever is in the Evaluation branch, copy it to the Current branch. Your test system(s) could update from the Evaluation branch.
Does anyone knows at what time exactly is the daily definition file being posted? This will at least help me to delay almost a day if I can configure ePO server to update the definition just before the file release time.
This is exactly what we do. We download new DATs to Current around 2pm GMT and then push them to distributed repositories around 4pm. Updates tend to be released around 6pm GMT, give or take a few hours. We download to Evaluation at 7, 8 and 9pm GMT for testing. If an update looks bad we have until 2pm the next day to stop the automatic download.