I have a Speed Twin and the manual says 16.000km or 12 months. I do not do 16.000km a year. I do around 7.000km. And I do change oil and filter between 5000km and 6000km. I am doing this around 40 years and never got any problem. Said that, even written at the manual, I do not feel comfortable in changing oil only in 16.000km even before a year on the road. And, despite everything, I will continue with my routine. It will not hurt my pocket and certainly will not ruin the engine+gear-box. Stay safe