The "pattied up" meat will be fine in the fridge, well-covered, for 2 days, so you can make the extra burgers later. You can also cook them all at the same time, layer them up as doubles, and chill. Then when you want a burger, just microwave your double cheeseburger patties until hot and build your extra burgers within 5-7 days. For food safety, make sure you reheat to at least 165F for 15 seconds.