I took my Janome MC 7000 in for servicing, the first time in 23 years and it cost me 60 dollars. The guy oiled the sponges in the motor, adjusted my feed dogs and re calibrated it.
I have a small compressor for upholstery work and once a month I used it to blow the lint out of all the nooks and crannies, other than that I didn't do anything special to it and I didn't get loops on the back when doing free motion. My Janome now enjoying retirement, watching my Pfaff sew. :)