It shouldn't be a problem, but I'd be worried about those mechanical timers accidentally being turned (i've done that)
This is why I love the digital timers. They're not THAT much more expensive, they have a battery so they don't forget the time when you unplug them (or stop counting like the mechanical ones).
If power goes out for 5 hours with mechanical timers, you will have to go back and correct the timers, or your whole period will be shifted by 5 hours. Just something to keep in mind. It should be fine.