Not sure what others do, but cleaning up stuck up noise in DOF (still mostly specular from highly reflective metals, glasses,etc..) for me can be big pain in Vray as well. I still use DOF in Post for animation.
Btw, you misunderstood me probably :- ) I said you could leave it for days....but there would no little (or no) change, ergo more rendering gets very diminishing returns.