When looking for a prospect, where do you stop considering ancestory as a big part of how it will affect it's abilities or attitude? Or are there certian paternal or maternal lines that are more potent for a less or longer period of time? 

I am not a good person to ask on pedigrees. 

But it looks like you have about 10 or so bloodlines that everyone tries to follow. 

I still go by what I am looking at right in front of me at the moment. What I see in conformation in the live animal. I don't believe everything I see in pictures. 

The mental part is all in the training and how it has been handled when raised.

The most able is worthless without training.  The most trained horse is worthless without ability.  Breeding is a predictor of ability based on lineage, but there are no guarantees.  For me lineage only matters in a prospect.  If I'm buying a finished horse, the only thing I care about is the subject horse.  Can it do what I want, the way I want it done??

Ability would include athleticism and soundness of body and mind among other things.

WELL SAID

SO MANY factors to figure in on this question but many feel that when a bloodline gets to under 10% it is a non---factor.

I agree with this. Love a good solid built horse and definetely have some lines I like better than others, but there sure are a lot of references of this horse can do this because theres so n so on the papers 5 gens back. Wouldn't think that would make a selling point?

Mind, confirmation, pedigree, color..... :)  If it's bred to the 9s and rides like a 3 legged table, then its just a legged table. 

An old timer once told me "you can't ride the papers".

I like a nice set of papers but the horse wins everytime.

I reach back as far as I need to, to find the lines I like.  

I tend to look beyond whats on the actual papers themselves to see the old stuff. I love the old stuff. So if it happens to be 6 generations back so be it, I agree with Whiteboy too. 

And will ad that it all depends on confirmation and care of horses too, how long they last or don't.  Proper hoof care, feed and training are so key. 

I look at about 5 gens back. Then I consider what I like in crosses in the pedigree. One name I like in 5 gens doesnt do it for me but a nice mix makes me happy.