I recently bought an 06 LT and have been concerned about the noises when accelerating. I've been riding a Harley Electra Glide for the last 17 years and am not used to the pinging type noises or the high rpm shift points being discussed.
You all are really shifting above 4K rpm?
Forget your habits from HARLEY or anything similar with high torque at low rev - having 2 big pistons and a tach red line around 5500 RPM.
The k1200LT like most 4 cylinders have a higher max RPM AND a different torque/power curve. The K1200LT engine is not comparable to a 4 cylinders on a Japanese sportbike of course. However the "official" red line on tach of a K1200LT is at 80000 RPM AND the torque curve PEAK is at 5250 RPM for 2005-2009 models (was 4750 for 1999-2004 models)
SO... you have to work with the caracteristics / power / torque curve of what you ride. If you need pulling power you need to shift near this 4750 for 1999-2004 OR 5250 for 2005-2009. If fully loaded or on a big hill, a bit more RPM is even better because although you have reached PEAK torque, you have not reached peak HorsePower until close to red line.
Do not worry too much about 5000 or 6000 RPM for a long time if you want - this will cause much less wear or strain than shifting too early during acceleration (too early would be below 3000). In Germany, on Autobahn, they use these higher RPM for long period everyday.
OF COURSE, you have 5 gears to select, so one does not ride at constant speed on highway at PEAK torque RPM just for fun. It is OK ride at lower RPM to cruise at constant speed. But if you have a big hill or need power to accelerate to higher speed, you need to use the RPM properly (or get a "feel" for the engine after a while without looking at tach).
P.S.: if engine is properly tuned (valves, spark-plugs, air filter, fuel filter...) it will NOT "ping" when shifted properly. If shifting at too low RPM OR using cheap low octane fuel, it might do some pinging so you have to be very careful to listen for these signs - on the long run this will damage the engine as there are no "knock sensors" to compensate on these K1200LT.