I have never had mine adjusted except at purchase from the dealer and it is still 95% in tune 30+ years later.How do you know? I've setup a lot of Linn LP12's and I would wager to bet that yours is in need of a tuneup, (probably many years ago). You would be surprised how much of a difference it will make.
These things age and go out of alignment very gradually over time. Our ears get used to this gradual change.