AP style - hourlong
It's one of those small but satisfying changes in the AP Stylebook -- AP finally has removed the hyphen from hourlong, making it consistent with all the other "longs" -- yearlong, weeklong, daylong.
I had a small hand in originally having all those included in the stylebook many years ago noting, when I was an AP editor, that we had lots of variation on the wire on the terms, some of which were in the book and some of which were not. It always puzzled me why AP went with the solid forms on all but "hour-long."
So, no longer need we remember that little variation -- all are one word now.