It was an interesting experience. I did 2 hides that had been previously fleshed and dehaired, and then dried for storage.
The first one (a small yearling) turned out great, but the second one was a disaster. It was an older, larger animal. As hard as I worked stretching it as it dried, it just ended up stiff as a board.
So I spent a few hours thinning the hide, and soaked it in water for 48 hours or so, stretching it periodically until the hide was white and fully flexible all over.
I then soaked it in a new batch of soap solution for about 5 days. Almost twice as long as last time.
I then rinsed it and wrung it as usual. This time the hide turned out great.
I'm glad I had this experience because I learned a lot.