You will see progress stop and the trays will stop fitting properly. For the best and quickest results, you need to wear them day in and day out and only take them out to eat. While not wearing them for a few hours won’t affect greatly your treatment, it’s best not to skip on wearing them, as the process will take longer and you will not get the results that you were expecting. If you want a beautiful smile and straight teeth, you will want to follow the instructions that you receive.