Good point. I wonder if something was wrong at the hotel if a bunch of people physically needed to visit the front desk at checkout.

I only threw out Mon-Thurs since those are the typical business travel days and probably the most common in/out days at the standard city or suburban Hilton/Marriott/Starwood/whatever. I doubt the March 31st date significantly contributed to unusual check-out activity.

If Hilton had historical data showing this to be true, I'm convinced they'd make the promo end one day later since it's certainly not in their interest for you to hotel-hop unnecessarily.