Kickdown adjustment from the horse's mouth

A shift kit changes the feel of transition from one gear to another via changes in the valve body when the kit is installed. If the factory adjustments described in that video needed to be any different the difference should be detailed in literature supplied with the shift kit.
I'm not going to say a shift kit shortens trans life. I don't know that to be true.
I will say installing a shift kit suggests that to the user, the feel of the shift is more important than trans life.