It's more dependent on the number of people clicking your links than the number of posts you make - and then, I suppose you could get a pretty good conversion rate if the product is extremely relevant and solves the question being asked.

I've never posted affiliate links there though, this is just general stuff.

Are your answers being chosen as the best answer? Long ago when I was working for a client with high value services ($20-30k a pop, medical stuff) I'd hire people to provide answers on yahoo with our link (not an affiliate link, just a link to our site) even though the links are nofollow - I think the key is to be selling high value products though.

it all depends on the niche really. if you can find questions that no one else is answering, you will get a lot more traffic to your affiliate product. if something is saturated, you would obviously get little to no sales

Thanks for the nice answers, very much appreciated. I have a clearer idea of what I should be doing now.