It sounds like you have it figured out Al.
There is NO constant in SEO. It is and always has been fluid.
The only thing that is a constant is good content. The value of links may change. The type and quality of links may change. The neighborhoods that you have linked to may change. But the value of good fresh content remains solid.
There are times when you have (or think) you have an algorithm figured out. If you do it gives you a competitive advantage. You then must have the resources available to quickly make the necessary changes. If these changes are not made swiftly you will be working on an old algorithm. If they are made quickly you can take the advantage until the algorithm changes again and then you start the process all over again.
It’s much like having a radar detector. Every time a new radar detector comes out a new radar system comes out to make your new radar detector obsolete then a new radar detector come out …. And the process continues to repeat itself.
Again, the only constant in SEO has nothing to do with SEO. It is content!
~Mack