Just a 57 gallon tank, which I am sure works out to a more sensible metric something number in its native Germany. Having the compressor run every 30 minutes for 45 seconds or so isn't actually a bad thing for my type of compressor (twin screw). The oiling system actually works better when the compressor is hot, as it vaporizes the water that would otherwise contaminate the oil, so making sure that it runs every once in a while is preferred.
I could easily fix most of the parasitic leaks that are in the rapid-air parts. The tougher ones are the quick coupler seals and swivel joints in some of the coiled nylon hoses that I have. Those are just crimp joints with O-rings and there is no way to tighten them up. As a rule, the bigger the system, the more parasitic loss; so much so that industrial compressors in factories and large shops run continuously, as there is simply no practical way to seal a system with hundreds of junctions and connections. All the printing plants I worked in had compressors that ran all the time, even when all the presses were not running. Granted, it's far from efficient, but it is just a practical reality.
K