Haha, I had something the same but with Empire. I thought Yoda was going to kill Luke and couldn't understand why Lando betrayed his friend. Still wanted to watch it whenever I was allowed to choose what I wanted. Not even going to try and put a number on the amount of times I watched those videos from the blue box. I don't think there's any set age and if there is it's something the individual has to decide on. I wouldn't feel right setting an age, as I can't really remember how old I was. If my future child can understand the words enough to question them and ask me questions, it's fine by me.