My V6 would warm up fully in less than 5 minutes of driving. The gauge would start to move within a 1/2 mile. You can check to see if the lower passenger side hose starts to warm before the car reaches 190, if so, the thermostat is not fully closed.
The downside is that it's very difficult to change the thermostat without removing the timing belt. The thermostat cover tends to break down over time, it's a good idea to replace it vs finding out it leaks after the install.

 

My B5 Audi A4 V6 had a stuck-open stat when I bought it, same warmup issue. The part is inexpensive but the labor is the issue (as PZ noted). The problem with this is that the engine runs in the inefficient warm-up program for too long, wasting fuel and allowing water to accumulate in the oil.

 

Maybe it pops up easier in colder ambient temps, but when mine failed open in the winter, it kicked off the code P2181. The ECU noticed that it was not coming up to temp fast enough (I wish I knew the threshold) so it set a code for cooling system performance.