If it isn't broke, don't fix it....works for me. The quote to service machines is $150....I save the money for my next machine.
I oil the wick and shafts on all my machines and, of course, vacuum lint and threads. Once every few years I take off the bottom of my machines, oil where ther is metal moving joints.... check the grease areas and put back together. Most machines do not any additional grease. If you have old hard oil somewhere, someone did not use pure machine oil. Also the grease I am referring to is machine grease that does not turn racid or hard over time. Don't be afraid of your machine. We are not messing with the computerized areas. If I have a major problem with parts or computer board, I would take it to the shop.