32 hours and counting ... still quite smooth running. Doing very frequent backups in case I mess something up. There's no way I'll be able to include everything I'd like, so tomorrow it's going to be lots of hard decisions - but still adding new stuff to my TO DO list!
EDIT: Now doing an end-of-the-day build to check for performance and memory issues - I think I might have gone a bit overboard with the scene size ....