Longines watch servicing

[Warner12]

Really sorry if it's irrelevant question.

What is involved in an Longines watch servicing, and how often should it be done? What are the typical costs of an Longines watch service, and is it necessary to go through an authorized Longines service center? Can owners perform basic maintenance on their Longines watch service at home, or should they always be serviced by a professional? What should owners look for in terms of signs that their Longines watch needs servicing? What are some common issues that can arise with Longines watches, and how are they typically resolved during servicing?