Hydros should be the least of your worries. Just take your tanks to your local fire extinguisher company or welding gas supply store. Both will either have their own in-house hydro tester or a relationship with another company who does all their hydros at a bulk rate. I do all my own visual inspections (PSI/PCI recertification pays for itself if you have even 6 or 7 tanks), O2 cleaning, & valve rebuilds, and take about 20% of my tanks to the local fire suppression vendor each year for hydro at $20 a tank. Maintaining all 30 or so of my tanks only costs about $140 per year (< $5/tank/yr). I have also recently purchased a nice used compressor for $1600, plus about $200 for a supply of new filters and other consumables. This will allow me to fill my own tanks with air for next to nothing after initially amortizing out the initial cost of the compressor. I figure the first 200 or so fills should cover it, at the $8 per fill the LDSs around here would charge me. I'll still go to them for Nitrox, at least until I build myself a blending stick and buy a cylinder of O2.
That said (and to address the original topic), I have about 8 tanks that are 2250 with original hydro dates in the 1970s, and nobody has ever hassled me about why I would want 40 year old tanks rated to a low pressure. For the same price, I'll take 8 steel 72s over maybe 1 HP 120 every time.