John, I have poor painting habits. I enjoy assembling and detailing, don't like painting, so, I procrastinate. As a result, refilled the tank 2 times in about 3 years. Maybe another user of this type system can give you a better idea of fill frequency. It all depends, I think, upon frequency of painting. But, for certain, no water trap is needed as there is no water (vapor) in the tank. No spitting nor white spots on a paint job! And that, to me, has been worth the expenditure to relieve the frustration.