According to the owner's manuals, the 500 requires oil & filter changes every 15 hours. A new piston every 135 hrs. 690 requires oil changes ever 10000km (100hrs at 100km/h) and a new piston whenever. This is why the 500 is higher maintenance. Similar kinds of change intervals for other maintenance items. Lots of people do different intervals or say the published intervals are for racing only. Using a different interval than the manual is a personal choice. I change the oil on my 350s every 15hrs. Lots of guys think I am wasting my money, but I hve not seen any proof yet.
Personally, when I think of "maintenance", I never count the farkles or the improvements to the bike. Maintenance means things like oil, filters, grease, and other wear items.
When I had my 2014 690 I think was getting 250km to a tank, not quite sure though? I also carried a 4l roto pack, so I am not 100% sure. Small tank on the 690 was a pain.