CCM using the BMW 450 engine (.9 L Oil capacity) have a several thousand miles between oil changes - The modification they make is to limit revs.
The 500EXC has so much grunt through self discipline you can do the same that plus which a new clutch cover it will hold 1.4 L oil so it’s not or unsafe to extended the range and that range can be based on what’s available - Need to do some big miles before you can get some good oil then just peg it back on how you ride it.
I changed oil half way around on Mark/Tim’s Morocco trip - I needn’t have bothered it came out very clean but thinking back that’s not surprising as most of the riding is on the pegs bumbling along at 40 - 50 MPH
That’s the other great thing about the 500EXC, fuel economy - Getting 70 mpg plus is not hard
In fact when I was looking for a KTM it was Martin at Torque Racing who recommended the 500 and that was one of the reasons - When he services bikes on Rally’s one of the jobs is filling up - He said it’s very noticeable how little fuel a 500 uses compared to a 450 and others.
Yes the can be brutal but they can also bimble
I have a 13 500exc which is brutal but also thirsty on fuel. I've run out twice.
It's great fun and I've seen 100mph on the speedo which is interesting on the off-road tyres