A bit tricky to answer. For one, no, Audi does not have a heat pump. I have the cold weather package and here in January in the Portland, Oregon, area a temperature in the morning might be 30F. However, my Audi is in a garage, so my starting temperature is maybe 40F. On a couple of occasions I used the MyAudi app to set a timer so that the car was fully charged and the cabin conditioned (using power drawn from the wall) for comfort, and I assume some battery heating as well. My understanding is that this ability to heat the cabin even when the car is turned off (and to set a timer for it) is available only with the auxiliary heating unit from the Cold Weather Package. On the occasions where I started out "cold"(no conditioning) the car would initially hemorrhage miles (or KWh) until I got the cabin warmed to a comfortable temperature. It took maybe 20 to 30 minutes before the energy consumption dropped to typical levels. If I did preconditioning, consumption dropped to typical levels in 5 to 10 minutes. For my Oregon driving, I would say I lost maybe 15 miles worth of charge by not preconditioning. If I were starting from being parked outdoors or in colder weather, I imagine the benefits would be much greater.
How long does the preconditioning cycle take? If you start it manually from the MMI screen, it will run 30 minutes, unless you turn it off. I don't know how long it takes to reach maximum benefit. This MMI start optiion is useful, too, I understand, if you are at a public charging station in the cold and don't want to freeze while charging your vehicle. Myself, I have always activated it using the timer. In that case it starts up shortly before the car is fully charged, which I set to complete by my departure time. Generally when I go out to the car the heater is still running.