It is amazing how much you can save by learning the different ways to clean your own machine. I have a Husqvarna Platnium 750. I've had my baby for 3 1/2 years now and I have YET to get it serviced!!! I take alot of my machine apart (which is not alot actually) and clean it myself.
Last week I went to a maintenance course for my machine and I learned sooooooo much more that I wasn't doing and know I have saved myself alot more money. Yes I even learned how to clean up those pesky nicks that the throat plate gets when the needle hits it (well the tiny ones.. when there are bigger ones, then yes it must need to be replaced.)
I teach my students how to clean out their machines after every course. You should clean out your machines after every project or every 12 hours of use. Change needles regularly,
timing issue.. well that is something that the technician would have to play with.. that one I don't know, but I do know how to detect the signs of a possible timing issue.
Wow that is big money some of your are having to pay out for servicing your machines. ouch.