What point are you at in the course? As above, it can often be a good thing to get a different point of view from a person from a different background. Not to say one opinion is right or wrong, but a different way of looking at something can often develop your understanding and broaden your own opinion.
Changing instructor is very common, at a lot of schools students will end up flying with whoever is free on a particular day and if they're not careful will fly with a different instructor each lesson!
I've only ever taken two students the whole way through the course without them flying with anyone else, most student I have either flown the first half or the second half, sharing the workload with someone else or inheriting them or passing them on due to instructors coming and going.