Be Ready to Downgrade
This is extremely important.
Once the iOS 12 update is released you'll have the option to downgrade back to iOS 11.
Apple's closed off the path to older versions of iOS 11, but you should be able to downgrade to the most up-to-date version. As of right now, that's iOS 11.4.1. Apple recently closed off the iOS 11.4 downgrade option.
The ability to downgrade to iOS 11.4.1 won't be available forever and that's why you should get familiar with the iOS downgrade process ahead of time. This way you'll be ready to make the move if needed.
Apple typically closes off older updates soon after new firmware is released to the general public. The company won't give any warning and once the loophole is closed, it's closed forever.
This article may contain affiliate links. Click here for more details.