Oh goodness. We get this all the time. DS is 5 in just over a week. The week before half term, he talked the whole way home, like, 15 minutes straight. He didnt even stop to let us answer his questions. Then there are other days when it's like someone put him on fast forward. It's insane. We also have days when he is just meh. And barely moves. I think the crazy behaviour for him is once he has passed tired.