The Market dictates what is too much, Why should we be worried about natural selection? The Market can't support that much books then they just get canceled. The weak ones just fall off .The only people who worry about too much books is people who are favorites of specific characters and won't read anything else. Then it becomes a problem which specific book is being canceled. If Market can only support 5 ongoing books those will be the ones to make it as simple as that. Hopefully the 5 best books or whatever the number is have on your favorite character.