The best way to not want the new shiny thing is not to place it in your hands in the first place. Just decide that the S23U is still plenty good enough and move on mentally to the S25U.
This is absolutely the best advice BUT I never follow it.
The way I see it is there really is no downside to a pre order with trade in. I have a few days I can compare the two devices side by side. If I don't like the new one I can send it back and keep what I have. No harm. No foul.
That is the only way I personally will know for sure. And if I do like it then I scored the best deal I will find for several months. If I don't then it just goes back.
The problem with this is that you are tempted by shiny and new and can end up with a newer yet worse device. I have done so a few times. But if you have a key list of things that are important to you then if the new device actually has at least three major upgrades then it is most likely worth it.
I mean the s24 ultra this year seems pretty sweet. The flat gorilla armor glass with much better scratch resistance and anti reflectivity. This in itself is pretty huge. Different camera array that has potential to be better than s23 ultra or at least very close, and that Titanium frame.
Honestly for me if I was getting the s24 ultra this year it would all be about the screen. The phone design is just about perfect otherwise and am glad they didn't change. What I would like to see in the next Ultra is a 6000mah battery. With the upgrades made this year, much bigger battery, same design and footprint, better camera sensors. That would be my ultimate Ultra!