Hey Doug, with regard to engine rpm at high speed, I really wouldn't worry much. On my recent Oregon-Washington tour on the SWing, I was running 65-75 pretty consistently, with occasional bursts to 90 or so (passing trucks, for example). 75 mph gave about 6200 rpm, with another 2500 rpm headspace to redline. The SWing will do this all day every day...that motor is made to rev, it doesn't hurt it all and it doesn't feel strained. Engine longevity, with the SWing at least, is not a problem even at high rpms, because the engine is designed and built for that kind of use and there are many folks over on the SWing websites reporting bike mileages at 50-100K without any significant issues. I suspect that the Burgman 650's engine is very similar in that regard.
On the BV, it runs down the freeway at 70-75 and doesn't even feel like it's breathing hard. It's not fitted with a tach, but one is not needed, in my opinion...I found that pretty surprising, because I owned a conventional single cylinder motorcycle (Suzuki S40...650cc thumper) which was all out of breath at 75 indicated and I really couldn't get much more out of it. I wasn't really expecting the BV thumper to be so composed.