My Janome has a little wick in the bobbin area, that's supposed to be the only user-maintained place to oil the machine; and my dealer told me that I shouldn't even do that as they will do it for me when I bring it in for an annual check-up.
But now that I'm past my first 2 years and those checkups are no longer free, I think I'll be putting a drop of oil on that wick every 6 months or so - I will probably not bring the machine in every year. Maybe every 2nd or 3rd year!