In the scenario where you've put in an initial set of orders and saved them, and are then trying to decide whether to change them up and whether you have time to make all the changes that need to happen together, it works out pretty well. Make the mass changes you want, double check them, and click Save again. If it is too late, then none of the changes take place. If it is not too late, then all of the changes take place.
What can catch you up is if you have your initial orders saved, and then plan on changing several units and you change some, save, change the others, and then when you try and save you've run out of time.
Bottom line, when changing your orders, only save when you are happy with the orders going through as you have them when you click save. You may or may not have time to make further changes.