They do support the rollback for a short time, usually about a week as you mentioned. You can download the previous version and install it. You do have to restore to do but it is possible until they stop signing the release.

I only bought the 2 because my wife wanted the Ultra as well so I gave her the U1 and for the U2 for myself. It works great for her. We’ve been snorkeling in the pacific and Caribbean with them. I’m currently living in Ecuador and have the altimeter is a nice feature since Quito is at 9k FT.

The max time anyone should keep a phone is when Apple no longer is maintaining the OS version for that phone. That’s usually one major version from whatever the latest happens to be. Beyond that you’re risking your own online security. Too far back and the device likely lacks even the necessary certificates to access much securely. The more and more we move to SSL for everything more important it is to update the software.