I've only changed the oil a couple of times in my compressor in the nearly 30 years I've had it. It's a compact portable Superior, which I was told at the time was an Italian made compressor. Don't know, don't care, the thing has seen extreme use and working conditions, and other than a little dirt and wear, it runs like new. The only problems I've had with it is having to replace the shut-off switch twice. I try to keep the tanks drained, but for some reason that gets neglected frequently. I don't use it as much or heavily any more, but in my construction days, it was used almost daily for everything from installing trim to framing houses to blowing drywall texture.
Oil still looks great, smells great, and is less filling . . . no wait, that's not it
feels great, no grit, no issues.