GAJoe, you'll love the 250z, I had one in .25 for a while.
Is this your first compressor ?
As you probably already know, Bill @ Target Forge has some good videos showing maintainence and overhaul of the various GX compressors.
I bought the T handle Allen set by Eklind that he recommends, they come in handy everyday for scope ring screws, etc.
His syringes of grease look handy but are spendy for just a couple ounces of lube.
I bought an 8 ounce tube of Lucas White Lithium Grease for $10, now I have a lifetime supply.
When I get some more time on the GS3-I I'll open the cover and check the piston ring and cylinder walls and relube.
Do a dead head test when you get the compressor, and write the time it takes the compressor to build to say, 2k and 3,650 psi (your 250z fill ?).
I wrote those times on a piece of painters tape and stuck it on top of the compressor.
Down the road you do the dead head test again, and if it takes significantly longer to reach 2k and 3650, it might be time to open up the cylinder and check the piston ring and grease the cylinder.
Bill has a deal with GXPump to sell basic parts, easier than getting the parts from Taiwan.
The other thing worth doing is keeping track of the run time, either with an hour meter or keeping a log in a notebook.
I had a $14 stick on hour meter from Amazon but it would come on when walking across the room, and turning down the sensitivity didn't help.
Fortunately I kept a notebook log as well, as the cheap hour meter read 147 hours when the compressor actually has only 6 hours of run time.
There are some hour meters that you have to hard wire to the circuit board that should work better than one that is vibration only.
The good hour meters turn on and off when the electric motor runs.
Bill sells one that sounds easy to connect for us non electricians. It has the correct pigtails to just plug directly to the compressors circuit board.
I have no connection with Bill and have never bought anything from him.
Part of my reason for buying a GX product was the product support and parts availability.
I don't consider a $330 compressor that I only run for a few minutes a month a disposable item.
Some guys say they just throw away a $200 compressor and buy another.
A guy another forum says he routinely fills big Carbon Fiber tanks with his CS3.
He shoulda bought a bigger compressor for that.