And the reason you don't render true DOF, is because render times or flexibility of post?
Both i'd say, especially because I work that kind of projects not from our office but from my home pc which is threadripper 1950x OC so i do not want deadly render times and I change my mind every hour about f/stops :P
true DOF is fun though, you can play with blades etc. like the one below. Trying to make you feel dizzy