Hammer, good call.
If a regular / local hydro test can't be done every 5 years, and the tank has to be sent back to them,
I am with you.. It makes it a bit more of a hassle to have to deal with. You also saw what I did regarding the PA tanks..
I almost got one of them myself - Until I took a peek at their born on date.. Nope, they were too old IMO too.
Those same tanks can be found on eBay in surplus - NOS [New Old Stock] every now and then from different sellers,
and the last time I saw them, they were years newer than the ones at PA.
Anyways..
If your tank isn't cf, and you're to the point that you're not quite trusting it 100%, do what you suggested..
Remove the gauges, etc. replace the o-rings, and just reuse those on a new[er] tank. That's what I would do.
I just got a Very Nice 88 cubic foot carbon fiber tank brand new on eBay for $459.99 - shipping included.
It is a DOT approved version, and I was Very Impressed! [I'm a very critical / picky person - OCDish] =D
I think I had another $80ish into the gauges, hose, adapters, etc.
In the end, it still came out cheaper than any of the other fully assembled ones that I could find online,
and everything is brand new.
In your case, if you reused your gauges, you'd only be out a few bucks in o-rings,
and would only have to cover the cost of a tank.. Saving almost 100 bucks, so that's cool!
I work with metal and weld, so, no matter what sort of Metal tanks I have/find, I usually just keep them laying around..
I've converted things like air compressor tanks and fire extinguishers into mail boxes, etc..
There is always another use for something..
Sam -