Don't worry about the pressurized air reservoir (not in a production SamYang, and most other bigbores anyways). After all, they are designed to take it. Many bigbores can be left charged indefinitely, as most are safety tested to over 2-3X their recommended fill pressures.
With the SamYangs it is recommended to reduce the charge to about 1500psi before storing for long periods of time due to the material/design of the exhaust valve stem. It won't blow up or anything if stored at a higher pressure.....still safe; it just might develop a leak in the exhaust valve, and leak the air out (usually very slowly).
Main problems I had with my tuned 909 was the breaking of SEVERAL cocking levers. An enthusiastic machinist took the problem on, and after I tested a few prototype lever designs he sent me he ended-up building a boolit-proof, quality one piece steel lever he is now offering for sale.
I also had a one-off custom stainless steel breech sleeve cover made due to the extra power of the tune blowing out the stock sleeve about 4-5/1000's. I was blowing a lot of o-rings out from under the sleeve, and in order to fix that you have to take the barrel off to get to it, and re-sight in and everything. I don't know anyone offering aftermarket breech sleeves.....might be best off having the machinist doing the work have the barrel on hand for precision measurements/adjustments.
I have always used a HillPump to fill mine with air. For about $275 you get a rebuildable pump that will provide a lifetime of propellant. If you don't want to work that hard, 4500psi CarbonFiber SCBA tanks make things much easier (if you know a firestation/paintball/scuba shop nearby that will fill tanks that large to 4500psi, or own your own $400? ShoeBox air compressor).
Hunting with bigbore airguns is a hoot. Plus target practice/plinking is cheap.....like 12cents a round in .45 (750shots .45Colt shipped to my door for $90). .357 is even cheaper than that.
I've killed ram, boar, coyote, bobcat, nutria, etc with my power-tuned SamYang 909 .45 bigbore airgun using slugs anywhere from 154-260grains. Check my post history for more info on bigbore air rifles, and some hunting stories.