My own way of writing is very meditated and, despite my reputation, rather slow-moving. So I do spend a good deal of time contemplating endings. The final ending is usually arrived at simply by intuition.
The first sentence can’t be written until the final sentence is written.
I am inclined to think that as I grow older I will come to be infatuated with the art of revision, and there may come a time when I will dread giving up a novel at all.