I like gauges. Use a bluetooth OBD reader nearly 100% of the time feeding the Android Torque app to monitor lots of things, including the coolant temp, when driving.
The only times I've seen the coolant temp exceed ~190F is during DPF regens in the summer (on hot days during regens the temp can hit ~200F) or after several back to back 1/4 mile pulls.
Winter time (for you Southern folk I'm talking about temps below 10F) for most driving conditions I've encountered the engine struggles to maintain more than 180F temps unless one covers the front grills.
2011 335d 11.8 sec 120 mph 1/4 mile NHRA certified track
2004 Ram Cummins with lots-o-mods