I agree with Ev...focus on that nurturing good
feeling and do not worry about when to quit. You
will *know* and it could very well be that Jacob
will wean himself and it will be you left feeling
like you just lost your job :)
I do not remember my hormones being out of whack
either and I nursed for 14 months. My daughter
weaned herself.
Also, there is no need to buy a book. If you google
"Weaning" you will find more articles than you could
ever need.