In some languages I only have one teacher, in others two. It depends on their timeschedule and how pressed I am to learn.
It also depends on what they cover best. Some teachers are excellent in teaching through conversation but they don't cover my needs in grammar and vocabulary translation. Others are too focussed on their books but they are great with grammar.
So, I try a few, pick the ones I like best and have lessons with them.
Most times their teaching mateial doesn't overlap.