I usually shift no higher than 4000 rpms on my Ninja 250 around town, and i have my bike geared down to 2.60 final drive from the stock 3.21, plus i have taller than stock tires... I accelerate a little faster than 18 wheelers normally do.
I think you should address the carbs if you are really worried about it. I dont know how the gs500's are, but the ninja250 comes rich from the factory. I changed the jetting a bit and it runs a bit leaner now, and performs a little better to boot.
The ducati on the other hand, its a little on the rich side .... because its a play bike
Heres a little write up about your carbs...
http://www.iwt.com.au/mikunicarb.htm