UA has few consistent patterns at all when it comes to their domestic schedule. The 45 minute layover you're talking about appears to be before the evening flight, which means that if that pattern sticks, you have any number of options if you are willing to add an extra connection (which, if you actually want to make your flight, you should).

From RDU, eastbound will be less distance but will likely involve a double red-eye, which tends to be an uncomfortable way to travel. A map from the Great Circle Mapper - Great Circle Mapper