it will take you a good 45 mins to walk from your arrival gate, queue at the transit security and baggage checks and finally make it into the shopping area which seems to go on for about 10KM. 3 hours isn't too bad there, it gives you enough time to look in the shops, have a wash and brush your teeth, take a leisurely cup of coffee, chain smoke 20 ciggies if you're a smoker
and then walk to your departure gate.