Sure, your system is higher capacity.
Well, do you need higher capacity? What for? If it takes you an hour to drive to the shop and back to get the fills, and the filling takes 30 minutes at the shop, then anything that requires less than 1.5 hours of your time to fill your tanks is a net win, right?
Even ignoring the cost.
If you want to fill a cascade, cool. I can do that if I want to. I'll have to add automatic drains, which I can do for about $200 worth of parts, or I can pay the rip-off artists $1,000 for the same thing on the compressor. The high pressure pilot valve is $100. The low-pressure solenoid valve to use as a "trip" is about $30. The electronics, including an astable multivibrator, power supply and relay can be assembled for well udner $25, and the rest is for miscellaneous plumbing. I'll also need to add a magnetic starter to the compressor and final pressure switch (to shut it down automatically); Graybar industrial supply makes the former and the latter is available from the same folks who make the pilot valve - about $200 for both of those. So a mag starter, final pressure shutdown and auto drains add about $500 to my expense.
4500 psi 444 cuft storage bottles are $350, brand new, DOT. If you want ASME 6000 psi ones you can get them too; they're more expensive but don't require 5-year hydros provided they're going in a fixed installation (which they should be.) Both come with valves for that price. You need to pay for the hardline, of course, the proper flaring tool (not the cheap Home Depot variety; you need the double-edge on Stainless tubing) or compression fittings, valves, and gauges to make the panel. You might also want to buy a fill regulator; some people want them so they can leave a bottle filling and not risk it going "boom"; the Tascom ones are about $250 if you can't stand babysitting your fills. On the other hand if you're going to fill cascade-style (and you should to make the storage system most efficient) you have to be there anyway to open and close the source valves for the cascade; in most cases, after the first fill or so the low pressure storage tank is no longer able to overpressurize the tank being filled anyway.
Alkin is not a "name brand"? Excuse me? Their blocks have only been used in various compressors by various manufacturers since 1960 or so. I think that qualifies; they're not "new to the game." They also use stainless for their interstage coolers, .vs. painted mild steel for most of the others out there. Not a big deal unless you actually live on or near salt water, or intend to ever use that compressor on a BOAT. Oh, its also 1200 rpm, .vs. 3000 for most of the other "smaller" capacity units, which means you can run it all day without overheating it.
Monitoring filter life is easy. The best indication of filter capacity being reached is humidity of the output air. When it reaches 40-60% (at pressure), you change the filters stack, or when hours of operation times output = rated capacity. If you do THAT, then LF hyperfilter stack will run to its full rated life. An inexpensive "eyeball" indicator will tell you when that figure is reached if its early.
If you're paying $250 for your primary (non-hyperfilter) media then you have a MAJORLY high output unit (or you're paying WAY too much for that media.) What is it - 10-12 cfm or thereabouts? Triple chamber parallel filtration, THEN the hyperfilter? That's a dive shop unit, right? 3 phase power? You can't get 3-phase power in most residential areas, even if you did want it.
1% digital gauges are just fine for PP blending, assuming you're using 3000 psi gauges. 1% is 30 psi. The difference between "real gas" and "ideal gas" laws is close to 30 psi for most PP blending. The difference between your fill pressure when you decant from the full bottle (and get cool gas due to adiabatic expansion) to room temperature is almost certainly more than 30 psi. Masurement devices that are more accurate than the other uncertainties in the system are an ABSOLUTE WASTE OF MONEY. With my 1% digital gauges, I am within 0.2% of intended FO2 on my final analysis. Since the tolerance allowed is 1% on "garden variety" Nitrox, my ANALYZER is probably off by at least 0.1% (1 count), and I would only go from 0.2% to 0.1% with a 1/4% digital gauge, the additional $300 is absolutely wasted money. Careful technique (e.g. intentionally adding O2 a bit "short", letting the decanted gas come back to room temperature and verifying the pressure, then making any necessary adjustment before proceeding) is far more important than 1/4% gauges. Oh, by the way, a 4" 1/4% 3000 psi analog gauge cannot be accurately read at a greater accuracy than 20-30 psi anyway, even with a parallax mirror (which it should have), so the 1/4% accuracy figure is true, but misleading to start with. (Cole-Parmer makes a perfectly decent 1% digital unit that is O2 clean and works great)
