I'll probably still get complaints sometimes, because they're monsters.
OT but...
Here is an idea. Take away the
big red button. Give them a
big green button.
Explain that they must press the big green button every hour to keep the systems turned on. Give them a countdown on screen in the last five minutes before shutdown, or maybe a quiet beep and a countdown on the button itself, on the iPad.
If the big green button isn't pressed, the systems shut down. You will still have some complaints, but you may find they accept this better than being asked to shut down the systems. They will quickly learn to monitor and press the big green button. Plus you
know the systems will shutdown one hour after use.
Pressing a big green button to keep the systems on is a positive action to give them something they desire. Pressing a big red button is a negative action to do something they don't care about.
Sometimes problems have to be looked at from an entirely different perspective.
PS: You may need direct support from senior management to implement such a system, and protect your arse the first few times the system shuts down while in use.