I used por 15 on my last engine. 25k miles, 1 trip from California to Michigan, 1 Michigan/ohio winter. I used degreaser and cleaned the block to do some work a couple weeks ago and it honestly looked as good as it did when I painted it. Also used por 15 on my frame and front axle when my engine was out, that's holding up great also.
Por 15 is expensive, and takes extensive prep work.