Everytime someone mentions TBIT walking time, this disparity arises.

There is variation base on fitness and age, congestion in the terminals (especially where you squeeze by a TSA checkpoint), escalators, what bags you are carrying / dragging along, familiarity with the route, traveling with someone, ... 15 minutes or 40 minutes are both extremes and not what most will do but the majority can do it in 20-30 minutes depending the mentioned issues. It is a bit over a mile from UC to TBIT and more to certain gates, especially T8.