Well, 2 out of 10 is according to me sufficient to be careful, and to avoid too-automated task.
But as @Minh_Nguyen ask : "Even as a first pass when mapping a line for the first time? "
If you know what you are doing, or as a first iteration all is fine 
My comment was more in the case of tools generalisation, and when connecting line to others thinks that you haven’t created (other lines mainly). Thus we should warn user somehow, because even if the end-tags are mostly pole, the few exceptions should not be removed !