I remember in high school auto shop the theory was the knurling allowed more oil in between and would counteract the lack of material... Just spitballing for conversation sake of course...
Absolutely it does. But my point is also true. Remember, the valves are the fastest moving parts in the engine. Lots of friction there. Reducing the surface area of the guides with NO other mods will make their life shorter, IMO. Now I'm not like the knurling haters who say they won't last anytime. I used to be. They last, just not "as long as" a new guide or liner, UNLESS roller rockers are included in the mix.