Rule of nap

While at my parents, James doesn't really exhibit many naptime symptoms, just drops off wherever he is.
However, at home we have the Rule of Nap- if he gets grumpy or has a crying fit- he has to have a nap. If he is reasonably happy, I'm fine with him not haivng a nap. Today, we had naptime symptoms and he lay down and was out. (if he lies down and just rests, I'm o.k. with that too.) I think we're having 'recovery sleep' from all the fun he had at my parents!
Also, something different from my parents is that he has to have a plan here. He needs to know what the next few days hold. I don't know if he just likes to plan or needs to be mentally prepared:)