I get my Vikings (actually all my machines) serviced once a year. The cost of servicing is minimal compared to the cost of repairs. My machines all embroider, which complicates the plumbing :lol:
You may want to check with a dealer and find out what kind of internal thread guides your machine has; if it has the wire thread guides internally, then the best thing you can do is to only use good quality thread. I had to have the internal guides in mine replaced because they were chewed almost in two. I bought it used, but apparently it saw a lot of lesser quality thread before I bought it.