I'm on many MC forums and many folks seem to want to change their OEM tail, brake and turn signal lights to LEDs, and I have to wonder why. I'm sure LED's lifespan is much longer than the OEMs, but I've owned 21 bikes in the last 20 years and I've never once needed to replace a single burned out OEM incandescent light bulb for the tail, brake or turn signals. Maybe LEDs are brighter but when I've installed them in my R1150RT's instrument cluster that wasn't the case and I eventually went back with the OEMs. And the reason I installed those LED bulbs in the instrument cluster wasn't because I wanted the cluster any brighter, it was because I had a couple that were burned out and it's a major p.i.t.a. to get to them. So while I had the bike ripped apart to do some other maintenance, I did the LED switch hoping to never need to touch the bulbs again, only to need to pull it apart again to go back to the OEMs because I could hardly see the instruments at night with the LEDs. But the turn signals and tail lights on the K1200LT are fairly easy to get to and you can easily find OEM style bulbs at any auto part store. I'm also sure the LEDs use less electrical power than the OEMs but the LT's electrical system puts out more watts than I'll ever be able to reasonably use.
Where alternate bulbs make sense in my opinion is with the headlights. I don't know if it doesn't get as dark in Germany as it does in the rest of the world but I've owned many BMW bikes over the last 20 years and all their headlights suck. I recently upgraded to a HID low beam and a LED high beam that I got from XenonDepot. Both were easily installed in my 05 LT and both make a huge difference on how much light hits the road in front of me.
To me switching out the turn signal and brake lights to LEDs seems like more trouble than it's worth, but it's your bike, time and money so do what you think best.