The average person has 30-40 hours of lessons to pass. I was ready after about 20 though, and some people may well take longer than the average. But at the end of the day if you aren't comfortable with your instructor then you will probably end up taking longer so yes I would change.
and to everyone arguing about men/women drivers, men are proven to have better spacial awareness etc, but they are more likely to be cocky and tend to show off once they've passed so they are involved in more accidents. So it works both ways