Should a merchant sign up to numerous affiliate networks?

Thanks for all your advice, we currently work with 3 affiliate networks - and we have quite complex tracking - so we should never pay for /or count duplicate applications. I'm currently working on  our existing programme, improving communications, introducing Prize Draws, attending network events etc. I'm hoping this will be more beneficial than simply adding another network to our programme. I do get asked from time to time - why don't we just get another network onboard surely more networks mean more new doors?? so at the moment I'm trying to gather evidence to convince colleagues that more networks is not the answer.