I think before reaching the advanced stage, it can be hard to work with many teachers if your priority is effectiveness. Topics will get repeated - not always a bad thing, but sometimes more time-consuming than worthwhile - and it makes it harder to track your progress systematically.
I also tend to have a favorite. I try a few teachers but I usually find one I really like and then other lessons don't seem as enjoyable. So for me, I try to stick to one person with occasional conversations with others.
Thank you all for your advices. I still cannot make up my mind. I think at the beginning it's useful to stick to one teacher to advance, though I started to learn my actual target language at an institute (intensive course) where we had several teachers native ones and non natives. I enjoyed it.
You are right Roy, maybe I focus to much on conversation, but I am quite advanced in grammar and have a BIG difficulty learning new vocabulary. Actually I am lazy, I do not spent time memorizing things, I never use flash cards for example, and I just adore meeting new teachers and reading novels, looking at films, trying to understand politics, having an insight in the life of people of different cultures concerning the language I am learning (ithe Arabic world is big, has along history and the actual situation is complex).
Thank you Guyomar for your post, it's good to hear from a teacher who is herself a (excellent) language learner. Unfortunately I am not at an advanced stage yet, because I am probably too curious and spend more time reading interesting cultural facts then memorizing vocabulary.
Sobian , I agree with you repetition is very important and that's the reason why I feel a little bit lost at the moment. I do not repeat systematically what I learned!
Mohamed (Simo) I try to understand the natives but it takes a huge time looking at films and Tv series.
Your note reads as if you are not focusing upon vocabulary and reading - only focusing upon conversation.
The problem with conversation is we quickly forget our conversations.
But, to answer your question: I prefer one or two main teachers, so they can focus on growing my capability. And several teachers so I do not learn only one or two accents and then get lost when someone with a different accent speaks.
Good luck.
Roy