"Mike, you want to discuss nature of humor. Are two types of jokes. One sort goes on being funny forever. Other sort is funny once. Second time it's dull. This joke is second sort."
The Moon is a Harsh Mistress, Heinlein
I read that years ago and thought, "That's going to be a really useful distinction once I have kids."
Well… yes and no.
It is a useful distinction! But it turns out that when you tell a slightly-ASD kindergartener that some jokes are "funny-once" and some are "funny-always" (or even "funny-more-than-once") it turns out that she immediately comes to the conclusion — and, I mean, it's a logical one! — that "funny-more-than-once" means funny again, RIGHT NOW. And right after that! And right after that!
So, we had a conversation about how the frequency of something that is funny more than once can change fairly dramatically. Some things are funny every month or so, but not any more often than that. That dinosaur joke that you look so adorable making? Is adorably funny more than once, but maybe wait an hour or so before telling it again. The bad pun that Daddy made is funny a couple of times in a row, but then after that you have to let it sit for a day before it's funny again. I know that you think how your schoolmate's calculator threw an error is the funniest thing you've ever seen, but in fact it is only funny once a day or so. (Hilariously, this happened yesterday; she then made sure to tell me the story again this morning.)
Baby laughing is adorable pretty much constantly, yes.
And we had another conversation about how Daddy might think something was always funny (e.g., stealing Mommy's food), but Mommy might think the same thing was only funny once, or maybe twice, or maybe funny several times but only once every couple of days or so. So it's person-dependent as well as frequency-sensitive.
AND this week we've been having an extended conversation on how Mommy might ordinarily find Thing X funny, but when Mommy is in a hurry and we are trying to do other tasks so we won't be late, Thing X is much, much, much, much less funny, and will be rather funnier once we are no longer in a hurry, or at least in the car.
In conclusion, humor is hard and Heinlein simplified it quite a bit :)