I don't think you should stick to one instructor throughout your training.
I did change some schools and flew with different instructors and I'm really happy as I did manage to get the best out of them and compare the worst. Even if they teach people they can have bad flying habits as wel as poor teaching methods and you won't be able to recognize it till you have tried more than a couple.
Probably one good thing is to fly with one instructor till you go solo. That was the standard at one of the schools I went to. After your first solo you can decide to fly with more instructors and if after a while you're really happy with one in particular then stick to it all the way if you like.