Halloween costumes and rookie mistakes

I understand that being a dad requires learning on-the-job. I guess that's why I sometimes get frustrated with myself for making rookie mistakes.

Case in point: my kindergartener decided a while back that he wanted to be a skeleton for Halloween. Well, about two weeks ago, I happened to pass a big Halloween store. Went in, looked around at the many, many costumes for sale (spoiler alert: Star Wars and ninja are going to be big again this year) and found a skeleton mask and gloves that are perfect for him. Paid about $15 for both and went on my way.

Then, later that day, I made my mistake. I gave it to him.

He loved his costume. Played with it over the next several days.

Now, a few days before Halloween, the thrill is gone. He wants to be something else.

How could I make this classic blunder? How could I not see that this was going to happen? After all, it happened last year, when he wanted to be Obi Wan Kenobi, and my wife made him a robe, and he played with it for the week before Halloween, and then wound up wanting to be something else (a hobo? half-Batman/half-Jedi? I can't remember) on the big day.

Someday I may learn...