As anyone who has an older machine knows, oiling and cleaning are fairly easy to do. In recent years, many manufacturers - instead of providing instruction on how to do it - have sealed the machines so you cannot do it - certainly not easily.
I have a Brother 1500S, I oil and clean routinely - oil every 6 weeks to 2 months, clean when I seen it getting dirty. Likewise with my old Kenmore which is even easier to get into (haven't had it "serviced" in the 42 years since I bought it) My Viking I can clean - although it is harder to get to many parts. I use a vacuum cleaner every once in awhile. They say it is "self-lubricating" and I take their word for it. I have paid 100 dollars for this kind of "servicing" only to note, that they have not done all that good a job - and it is a 5 minute job. . .
Were I to buy a new machine today, I would take into consideration whether you can clean it and oil it yourself. If not, be sure to add the cost of yearly cleaning and oiling to the tab.
That is one reason I bought the Brother which is my work horse.