I beleive he is talking about the lifter filter screen. He has a "96 EVO motor.
I check mine ever 10k miles but that is me. I do know if it clogs you know it because your lifters stop getting oil and start to make all kinds of racket.
With modern oil filters, I have never found any thing in the screen. With the old shovel oiling system and "fiber filters", it was a good idea to do it every oil change. Just MHO