I am happy to answer the actual question that you asked. In normal use, tonearms do not wear out, however the bearings are quite fragile on some models and mounting cartridges without removing these tonearms from the turntable can cause Brinelling (flat spotting) of the tonearm bearings due to the tortional forces applied by tightening the mounting screws. Once flat spotted the bearings will have to be replaced. Some arms also have fragile tonarm wire that can be problematic as it ages or is stressed. One of my arms is almost 60 years old and works quite well, so I think that most vintage arms should be fine.
Tone arm question
I recently purchased the Thorens TD 160 HD without a tonearm to fit in a custom built plinth i'm building. I need some suggestion on a brand and or model of a tonearm that will match the Thorens. I have a budget of 2,000.00. You can buy a lot nicer tonearm used, But do tonearms ever wear out under normal use