Great concept, but etas are off

I use waze as my main gps app and whenever eta would tell me a time (eg. 35 minutes to get from work to home) once I tap on it waze calculates a different eta (which is more accurate since it takes live traffic into effect). Waze would calculate to like 45 minutes which is a big difference when your app is suppose to give you eta and its off by 10-15 minutes. Please address.

Vidit S. about ETA - GPS & maps driving times, v1.3.1