Re-analyze face recognition each time you change a node?

I've just started using face recognition, it's amazing and I love it. However, I have a question. I've noticed that if I change a serial node that comes before the face recognition FX node, and then I go back to the FR node and I toggle the node on and off, there isn't a change- making me thing that if you change a preceding node it needs you to re-analyze the Face recognition FX. Is this the case? If I've already hit analyze once, then I change preceding nodes, do I need to analyze again? Or will it do what it needs to do when I render out?

Thanks