May have been mentioned before, but i have given my fh a quick clean after 300+ games since the new playfield swap. The white rubbers showed no discolouration to speak of, the pf was very clean, flipper rubbers were great and the cloth i used looked nearly brand new, not like a mechanics rag.
I can only put this down to new balls and ensuring the scoops and under playfield ramp were cleaned spotlessly prior to the pf swap.
A lot of people will clean or shop a game but forget about these areas. Put in new balls and all they do is pick up the carbon found inside these areas. Pretty soon the pf is dirty again.
Hope this tip saves a lot of time for people. Thanks