Like most things there is a balance. My club operated a primary and a secondary instructor who kept each other up to date with where I was. Both are very experienced and although I know they have their own way of doing things, they are happy to support each other's techniques. They are quite different personality wise but both incredibly experienced. I've learnt alot from both.
Nearer my skills test I went up with the chief instructor, who is totally different again (a bit more combative) to be comfortable flying with others before the exam (and I think my instructor was being tested as to how good my training was!
So I'd say using more than one instructor is a good thing, but six is bad, and you need to work out some way to deal with different instructions from different instructors, otherwise you'll be just getting confused rather than learning!