Take a plumber who wants ads running around the clock because emergency searches happen at 2am. The catch is what happens after the click. If nobody answers until 8am, you're paying for a lead that calls the competitor who picked up instead.
My view is to keep emergency keywords on overnight only if there's a real person or reliable on-call answering behind them. Otherwise, limit the schedule to staffed hours.
I wouldn't switch off-hours off completely on day one, though. Put after-hours traffic in its own ad group with a negative bid adjustment, so you can see how many of those calls actually turn into jobs once the team is back. Has anyone measured that gap with call tracking, or do most people just guess?