I have three GX compressors, two CS2 and one CS3. I use the CS3 daily and have had it now for a few months. I found the original factory grease is Reliable Lubricant's Bio-Food Grade EP Grease, and ordered some from them. I don't really think you need all those super expensive greases advertised if you keep up with maintenance. These compressors run slow and normally not for long times, they don't get hot at all, so a super grease is not all that important, and I'm not sure the RL grease isn't indeed a super grease. I've said a thousand times, I've never seen an engine or lubricated part fail from the wrong brand of grease, but I have seen failures from no grease at all. I don't know how the CS4 grease pot works, but greasing the other compressors that require the head to be take off is child's play and only needs done every 4-6 hours, so no big deal. The email I sent to the factory said not to do any maintenance for a year, but I don't think I'll go that distance. I don't have a need for anything more than the CS3, as I fill my six pcp rifles with it and don't use tanks or cylinders at all. I opened up my Brocock Sniper HR the other day for some repair and gave it a thorough inspection, not a single sign of moisture anywhere.
I do have two small inline water filters with both the cotton filters and desicant in them. When you include the cotton inlet filter, the small filter in the outlet and the filters I added, there is no way for any residual water to make it to the gun, and there is also no way any errant grease can make it to the gun either. These filters and the line added has increased the fill times a bit, but nothing earth shaking, and it's well worth the peace of mind. My compressor never runs more than 7-8 minutes at a time, and that's only when filling my 480cc Brocock carbon fiber bottle from empty to 250 BAR. All other times it runs less than 5 minutes tops, so it hasn't had any real heat issues. These compressors are designed well and if used with even a modicum of common sense, should last a long time. The good part is parts are readily available from multiple sources. I ordered enough parts direct from GX and had them in a couple days. If these compressors hold up as I expect they will with proper care and use, they will turn out to be the best buy in compressors yet. I have also had my HW100 .22 apart and again no sign of moisture, and I will be disassembling my HFT500 and another HW100 in .177 apart sometime soon, so I'll report on them when I get them done, but don't expect any problems.
I'd be interested in how the grease pot works too, and I'd love to have a CS4 even though I have no need for that sophisticated compressor, but they look awesome. I use the CS3 because I like the auto stop feature, but in reality, I don't mind using the CS2 and watching it as it usually is only a couple minutes.