I change the oil & filter every 5.000km (3.000mi).
The reason is that i think that ish't good for an engine (especially motorcycle engine) to run an oil for 10.000km (6.000mi).
Nowdays, most car makers advertise that their motors need oil changes every 25.000km !!! (like VW etc..) Have you ever seen how poor is the quality of an oil used for 25.000km ? It is something like a mix of water and marmelade... That's why i don't believe "marketing tricks" for low cost and long service intervals.
Personally i use the ELF moto-tech4, 10w-50 which is a step between semi & fully synthetic. Its main advantage is its price (6 euros per liter-"special offer").
I change it regularly, now i'm on 14.200km, in a few days i'll have 15.000km and i'll do my 4th change.. 1)at 1.000km, 2)at 5.000km, 3)at 10.000km and 4) at 15.000km.
Allthough i'm still thinking to put the fully synthetic Bell-Ray EXS 10W-50... but mechanic insists that this oil will reduce the clutches life...
P.S.
For me its a pitty when we spend lots of money for zorsts, suspension etc. and let our engines with the same oil for long periods.