@WarnerCrocker I prefer ‘update now, so I can catch if something goes wrong.’
I think the truth is, Apple would rather roll out the upgrades on their schedule, not yours, so as to control traffic jams, make life easier on their servers etc.
Saying ‘Tonight’ allows them to target the devices when they think you are sleeping, etc, not tooling around with the apps and bandwidth as it happens.
And that’s great if you live in a fast WiFi cloud, and trust their randomness.