I was under the impression that the "everyone else/default" rule is what applies to any device not listed in the wireless clients list and so if this is set to "everyday, all day" then anyone can access the network "all day, everyday"
This is correct, but it would only apply to devices that do not have separate Timed Access "rules" set up, assuming that the device has the correct wireless password.
In other words, if a device does not have a specific rule set up for Timed Access, then that device can access the network at any time, assuming they have the wireless password for the network.
Once you set up a "rule" for a device, the "rule" controls when the device can connect, and the default rule of "everyday, all day" no longer applies to that device.
Now....if you set up default rule of No Access.....then no device will be able to access the network unless they already have a "rule" set up that would allow them to do so. So, a device that might have the correct wireless password for the network still won't be able to connect unless a rule has been set up for that device.
Where users get into trouble.....we see posts about this all the time.....is that they set up a default rule of No Access without first setting up rules for devices that will be allowed to connect. When this happens, the user cannot access the wireless network at all to correct the mistake in AirPort Utility......unless he can connect using a wired connection.
A Soft Reset might be a way to get around this....but that requires that you change the password, which users may not want to do. A Hard reset erases all the network settings, so the user has to start all over again and set up the AirPort router from scratch. That's a lot of work. Same for a Factory Default Reset.