Render but make changes! Win

I remeber one of the devs claiming that it would be silly to animate output variables while rendering (when all things animatable arrived), but during a test render today I was scrolling through my output settings.

I noticed that I had to many samples on for anitalisaing, so I changed the value and my render times plumetted. Score!

What else can I do?
Well i noticed that I had made a node stack that was routed to a viewer but I had forgotten to send it to output. So I re-routed the nodes, to export the vector blur, to a Compositor out Node. Score!

It never occured to me to change stuff after I started rendering. Cool.