long time to warm up?

I've got an 06 2.0 A3 and I've noticed it takes quite a long time to warm up. Anywhere between 15-20 min of driving. Outside temps varied between -20 C to 15 C but makes very little difference in terms of warm up time. Thought it might be a thermostat problem, took it to Audi and they found no problem. They said the warm up time was probably normal but could'nt say for sure. Thanks. Anyway I live near a highway to get to work and I'm trying to avoid "opening it up" until the engine got to a proper operating temp as per the owners manual. Any advice?

The A3 2.0 warms up very slowly - about twice as long to get the water up to temp as the BMW and Volvo I own. It may have something to do with a larger block bound water capacity for the turbo and intercooler.