On all of my 3/16 I change all fittings every year, flush first. That seems to help move debris to the fittings, then change the fittings.
I tried Zap Bac and used them for 3 years but have decided to go back to CV2. I'm not scientific enough to be sure but fairly sure year 3 yielded less sap. Maybe it was just the season.
Mountain Van really likes them. Ask him what his cleaning method is.