I hate to say it, but the Wagner units are so inexpensive, that they are like "disposable" items. Other than replacing the filters (you'll pay more in shipping to get the filter than the filter itself), if you have problems, simply buy another...
I completely agree! Printers are like that too now. If you need a new printhead for Canon, you should almost consider a new printer as two printheads and a full set of inks will probably cost the same price!
I for sure don't need the the super expensive system, and since I won't be spraying much, I don't mind the air intake being being right on the unit versus several feet away. So it looks like the Double Duty model might be just fine for me!