Is it bad to keep Caillou waiting?

Caillou put in his order for Charred Lizard, Bat Wings and Slime Liver. My Advance Order Summary shows no deadline for this order, so I assumed I had as much time as I needed to find this stuff. Then he came into the store and complained that I hadn't gotten the items yet.

Does it hurt me in any way to postpone this order? Does he eventually run out of patience?

The only penalty for not filling his order is that he doesn't start being a regular customer - and from there, a possible adventurer contact - until after you've filled it.

... Oh, and technically he also takes up a 'customer time' slice when he comes to pester you, meaning potentially a lost sale because while you're appeasing him you can't take another customer's order.

Edit Almost forgot -- IIRC, his "complaint" dialogue also breaks any Just Bonus chain you might have been working on.

It does not hurt you whatsoever. Calliou may come in to complain, but he will pay up, just the same, when you finally get them in stock.

Conversely, if you have all three items when he first makes his appearance, he will be utterly flabbergasted, and purchase them on the spot for double his initial price.