Jeanne has just completed her 3rd single handed circumnavigation.
Her blog is here CLICKY
If you read it through you will see she had problems with her autopilots on all three. There were times when her wind generator was broken, both main engine and generator engine were U/S, the sun was not shining and her batteries were flat.
The back up was a Hydrovane which just kept on ticking.
If I was going on multiday passages I think I would fit one.