this was raised in the costs topic.
The question can be phrased two ways (note these pertain to a single dance style and to a long-term relationship, not a one-off visiting superstar):
A. Is it a good idea to work with multiple coaches at the same time
B. Should you change coaches and if so, how frequently?
A. I'm a one-coach girl
IMO if you have two coaches one is (in general) either better or suits you better. OK there may be some areas where the other is but I don't hink its worth it to have conflicting information.
B. OTOH I do think its a good idea to change coaches but again for me this occurs very intermittently - a matter of several years when its apparent that you have reached 'diminishing returns'.
I think it depends on the goal of the coaching. For example, at one point, even though I had one main teacher, I was also taking lessons with a few others at the same time. The main teacher for most stuff, but a second ( a guy with a hiphop background) to teach me body rhythm, a ballerina to help me with spins and hand/arm styling, etc.
And yes. I think that, when one reassesses her/his goals periodically, a change of coaches should be at least considered, even if it's immediately dismissed. One should always be as sure as possible that her/his coach is a good fit.