I can't say i personaly subscribe to this way of thinking. I think you can usually work out the content of a film by the Director/Actors/Subject matter and a book by it's author and style/subject. This way you can determine if it's worth your while, I don't think having the ending shown to you has to necessarily ruin the movie for you but I myself prefere to let the Director/Author do what they do and enjoy the ride. Some films rely on the ending more than others. I've never walked out of a movie theatre in my life and rarely turn a film off if i've planned to sit down and watch them. Even books i've not enjoyed i've ploughed through just because I think you can still take something from them. Weird because i'm not a maticulous person, in fact, far from it! Either way, you conversation reminds me of the scene from Harry met Sally that i quoted for Jake on the blog:
Sally: Amanda mentioned you had a dark side.
Harry: That's what drew her to me.
Sally: Your dark side?
Harry: Sure. Why? Don't you have a dark side? I know, you're probably one of those cheerful people who dots their "i's" with little hearts.
Sally: I have just as much of a dark side as the next person.
Harry: Oh, really? When I buy a new book, I read the last page first. That way, in case I die before I finish, I know how it ends. That, my friend, is a dark side.
Sally: That doesn't mean you're deep or anything. I mean, yes, basically I'm a happy person...
Harry: So am I.
Sally: ...and I don't see that there's anything wrong with that.
Harry: Of course not. You're too busy being happy. Do you ever think about death?
Harry: Sure you do. A fleeting thought that drifts in and out of the transom of your mind. I spend hours, I spend days...
Sally: - and you think this makes you a better person?
Harry: Look, when the poo comes down, I'm gonna be prepared and you're not, that's all I'm saying.
Sally: And in the meantime, you're gonna ruin your whole life waiting for it.