Many ways to take this conversation.
1) I have been guilty of the "If it sounds different from what I have now, it must be wrong". Especially when I listen to one system for a very long time. The brain eq’s and compensates to adapt to the current system. Assuming you like it and not wanting to change out of boredom, a new system will sound worse.
2) I have a method to avoid the "break-in paradigm" and keep things in the "first impression" phase. When I get a new component, I will listen the heck out of it, maybe compare to what I currently use, for a day and then put it away for a week or two. If break-in is a concern, I will let it play during that time but not listen to it.
So I have a week or two to let the component physically break in and also mull over what I heard. Maybe think of some other music to try to test it out better.
When I put it in a week or two later, I will see if the sound compares to what I remember and how I like it compared to what I currently use.
As an aside, I will often not listen to my stereo AT ALL for that week. Only listening to natural sounds and live un-amplified music. So my ears aren’t **&(*ed up with this "hi-end crap", haha, and I can go in fresh.