How are these, worth it? I take it I'd want to fill.with zeolite only, no carbon?
Agreed, several good points. My Yong Heng fills fast so long filters aren't a concern, other high-pressure air (HPA) compressors that take longer to fill, and thus risk generating more heat, the ability to hold pressure in long filters is smart. WMI recently bought one with 3 stages, charcoal, molecular sieve, and desiccant. Well satisfied, but PCPs don't care much about the air taste, so the charcoal doesn't do anything for me. Will try just the sieve and desiccant the next time.
Also keep in mind, these big filters represent a significant load on your compressor. It's like filling an extra (about) 60 cc tank, as far as I can tell from timing a fillup.
I solved that issue with a couple of valves, so that after the first fill of the day, the pressure would remain in the filter, while the compressor output, and gun filling ports, could be bled properly.