When I use mine, I oil it before I start a project and from there you can kind of hear when it needs oil, if that makes sense. So I would agree - about 6 hours of sewing sounds about right. It is not a sound, like "oh my, I better stop what I am doing and get the oil can." It is just a minor change that you can hear when sewing. So maybe if you have a very busy day, oil it when you stop for the day. If you haven't used it for a while, oil before you start.