How long should you allow your 2001 A6Quatro twin turbo to warm up? on 2001 Audi A6 Quattro

Especially in cold weather.

Asked by for the 2001 Audi A6 Quattro
Use the correct grade of synthetic oil and I would allow it to idle for a minute should prolong engine life.
Thank you. My son (who actually bought the car) believes you have to warm it up for at least 5 minutes (or more).He says if not, you will ruin the turbochargers, and then the engine.