I have been using West Marine Lube for the head pump. Until recently, infrequent use has been sufficient with pump working well. During the past couple of weeks, on a cruise with 4 people on board, I have been having to apply every evening with good results lasting only until the following afternoon. Does letting it set for about 8 hours instead of recommended 12 make that much of a difference? Head is 6 years old. Does the pump, plunger or something else have to be replaced periodically? again, thank you, Bob Pilgrim