Yong Heng oil change frequency using Seco 500?

Manual says after 50 hours for the first change and 100 hours or one year thereafter. Me, I change it when it looks dirty so an hour or so the first time and then I think it was ten or twelve hours the second and not at all after that as it is not looking dirty. But it's been near a year since the last change so it's about due for another one.