Its common practice among people who post here, but probably not in the "real world" of Universal visitors. Most people don't consider it because it seems counterintuitive to get a hotel room you won't use. But it can make financial sense. When calculating the cost, keep in mind that if your third person is over the age of 18, they do impose an extra person charge for the night so that should be factored into any cost considerations. But even still, its usually cheaper than buying two days worth of unlimited EP for each person. If you have an AP, there are often great AP rates on the rooms as well.