20,000 km... let's see that's (click-click-click) 12,428 miles. Not too shabby! The first year I had my SV, I put 15,000 miles on it. (24,139 km.) The next year, only 12,000 miles. (19,311 km.) Last year, only 8,000 miles. (12,874 km.) I got into woodworking last year, so that cut into my riding time.
Scuba: Since you like to ride lots of miles, take my advice and get a Corbin seat. They are very expensive, (Mine was ~$200) but they double your stamina. The BMW probably has a pretty good stock seat, but I've read bad things about the long-term ergonomics of the Honda CBR F4i seats.
Last year, I made road trip from Chicago to Franklin TN. and back on the SV. I took twisty side roads on the way down, (about a 16 hour ride) and interstates back. (8 hours.) I vowed never to do that again on the stock seat. So I think I'm going to do that again soon, possibly even this summer.
One last line of thought... You both wear helmets, right? Good. How about earplugs? Far too many people ride without earplugs, IMO. The windblast will damage your hearing in short order, even through the helmet. If you have ever ridden without a helmet, and later upgraded and realized how much quieter and less dramatic it is, it is the same step with going from no earplugs to earplugs. I use foam ones that you buy in a big box. At the very least, try it for a week. My bet is that you will not want to go back. (like Algebraic to RPN?...)
Frederic: Off the top of my head, I don't know what kind of wind protection your bike has, but I bet it is pretty good. The earplugs might not do as much for you as it does for the Scuba Diver and myself.
-Jeremy