Let me start off by saying that I can't put down in words *my* definition of excessive lining, I just know it when I see it.
When I judge and see excessive lining, I will make a note of it in my book for future reference to see if this activity occurred on every mark or which specific ones. If, during this excessive lining, there comes a point when my mind says "Come on, send the dog" and make an extra note of this.
I can only judge what I see and take that into consideration in marking my book. If I'm not the judge signaling the birds, I can concentrate more on the dog and handler and make notes if the dog didn't look toward a bird fall or gave the impression it wasn't following the fall of the bird.
It isn't up to me to speculate on the handler's reasoning for doing the excessive lining - thought the dog didn't get a good look at it, thought is was a difficult mark for the dog, that's the way he does it all the time in training.
Even if I had noted during the shooting of the marks that the dog didn't see a particular bird down, and then the handler started excessive lining on the same bird, I still can't believe that if the dog can't be lined up and sent within say 15-20 seconds, that another 30, 45 or more seconds is going to change the animals mind.
With my dog, this excessive lining only scrambles her mind to the point where she is convinced I've completely lost my mind. I try to get her as close to the line of the mark as quickly as possible and then correct as necessary to get the mark.