They drive me crazy. There's too many factors that make last minute design ideas a supreme headache. There should be a law against last minute design ideas. At least a law for a mandatory huddle to discuss it in detail. I pity the poor soul working for a last minute designer in film.
I love it when it's a last minute large format print! Or a last minute hero book cover. Let's get an ice cream truck! Forget clearances it shoots in an hour! It'll be awesome!!! (that was written in sarcasm font, in case you missed it.)
Inevitably the last minute design idea gets done in a hurry and looks like shit.
I eventually learned to stop running for them. The faster you run, the more last minute design ideas they have.
Wanna piss off your assistant? Call them when they're on the road and tell them they need to come back to the office to design a 24'-0" banner that shoots tomorrow :-)