Thanks Paul!

That could be a time saver!

Quote - > Quote - Interesting.  It must have used the cached SSS map from the first render.  It's a shame that there's not an 'official' option to reuse the SSS map...

I think you nailed it; the second and subsequent renders reverted to the non SSS style, although if I then do a render with SSS turned on, then off, it happens again.  

Something similar used to happen with soft shadows in Bryce, years ago.