The prepass was done in about 2 minutes and, after the first 2 rows of render buckets were finished, the forecast was for about 2 hours more. We all know that Vue's render time forecast is not very reliable but assuming it is, seems that DOF (at least in the case of my image) increases the render time in about 4 times. Like I said, it's slow but not impossibly slow. I can perfectly live with an 8 hour render (I typically let Vue render while I'm sleeping or while I'm at work and both take about 8 hours :-)).