I'm sure this is why but I had the same thought as GP. Under what circumstances would 24 hours be disruptive, but three days would be okay?
If you're using the iPhone as some type of IoT appliance, either time limit would be disruptive. But if you e.g. enable Guided Access, the phone will stay unlocked and so shouldn't reboot.
If you're using the iPhone as a phone, who the heck doesn't touch their phone in 24 hours? Maybe if you're on some phone-free camping trip and you just need the iPhone with you as an emergency backup—but in that case, I don't think Inactivity Reboot would be particularly disruptive.
How though? Users haven't used their phone in a day or more? How would they notice except for having to reenter their passcode which takes two seconds?
If you're using the iPhone as some type of IoT appliance, either time limit would be disruptive. But if you e.g. enable Guided Access, the phone will stay unlocked and so shouldn't reboot.
If you're using the iPhone as a phone, who the heck doesn't touch their phone in 24 hours? Maybe if you're on some phone-free camping trip and you just need the iPhone with you as an emergency backup—but in that case, I don't think Inactivity Reboot would be particularly disruptive.
Maybe Apple will lower the window over time?