Unless they are mentoring you on different things, in my opinion you should only have one at a time.
That’s because each will have their own ideas and style.
If you’re using two, for example, then the ideas could be contradictory.
That’s because no one has a corner on good ideas, and there are many ways to get the same results.
The key is to find someone who respects you, shares your goals, recognizes what you’re capable of, and who will stretch you.