I suggest that whenever Apple comes out with a new notebook that is better than the one you have, just buy it. This means buying maybe three computers every year, but this is the ONLY way to keep up and never worry that you don't have the "best".
Remember Steve Jobs? He had a standing order at the car dealership that every six months they were to deliver a new car to his house and take the "old" car away. Perhaps you can order a computer on a subscription?
But Steve was a billionaire, and cars were less than "pocket change" to him.
If you are rich enough, just buy every new computer. But if you aren't then you have to ask yourself. What problem is my current computer causing for me and what new computer will address this problem? In my case I use some 3D CAD software, and it required a version of macOS that would not install on my Mac. So I had to replace the computer. I had a problem and the new computer fixed it.