I was very poor as a student (I was a student for many years…), so I would make eggnog every year from scratch. My recipe is very similar to this one, except I only used rum (the bourbon and cognac were out of my reach):
When I make it these days it is very popular: I always get asked to make more next year! I occasionally make some at random times during the year. I don’t think I have ever bought any ready-made eggnog.