You will often hear you should service a mechanical watch every 3-5 years, or every 5-7 years. Many people even live by the idea that you should only service a watch when something breaks or is so far out of spec that it becomes annoying.

He used an example of a watch that had been run for 7 years straight without any servicing, and showed how the lubricants had dried up by then and the parts had begun to wear down. So obviously, for that watch, 7 years was a bit long to wait.