That’s a question I get asked a lot in my professional life. It’s not that easy to answer.

That’s why I usually ask first: How much do you play per day/per week?
With an average amateur musician, I usually get the answer: once a week orchestra or quartet, two or three times a week, 0.5-1 hours a week.
In such cases, I recommend a visit to the luthier every two years.

During the 2-yearly check-up, the following shall be checked:
General review
Are edges open, do you have to glue them?
Is the bridge warped, is its position right, are the strings dug in?
does the instrument need to be cleaned?
Are the strings okay?
does the sheet have to be re-upholstered?
Are the vertebrae still okay, or are they slipping, or are they too tight?
If you have your instrument checked regularly, you can make sure that everything is in place.