Mechanical watches do need servicing periodically, typically every 5 years. They are complex machines and need the proper cleaning and lublication to maintain accuracy and prevent parts from premature wear. Even if a watch appears to be keeping acceptable time, it still needs servicing if you value it and want to keep it running. Just like you could drive a car for years covering many miles, but if you don't get it serviced then sooner or later it will fail and you end up with either an expensive bill or just scrap. The old wives tale about mechanical watches not working if left not running for years, is because oils can dry up causing the movement to stick (not so common with todays lubricants), or if the watch is no longer water resistant due to the seals perishing/failing then moisture ingress can cause corrosion. Whilst initially the cost may be off putting, servicing from a manufacturer usually includes; full clean and lube, case refinishing, replacement hands, replacement seals, water resistance testing, and a 12 or 24 month warranty.