I also have a Viking, and when I was using it all the time, I just cleaned the lint out and kept my area clean. If I did not use it for an extended period of time, I found that it just didn't work right and I would take it in to have it cleaned good and serviced, but it the cost was about $69.95. I just tried to use it after 7 years packed away and it only sews in reverse. I took it and my Feather-weight to be cleaned and checked. I have had my Viking for 33+ years and I miss it.
Someone in my quilting group said they were told not to use canned air because it can damage the electronics in the new machines.