Back then albums were usually recorded in a couple of days. "Kind of Blue" - just another day in the office :)

I love his recordings, will be missed. There was a good interview with RVG in Tape Op 10-ish years back: http://tapeop.com/interviews/43/rudy-van-gelder/

If you are interested in recording, I recommend subscribing to Tape Op. It's wonderful, and it's free.