Like any machine, a mechanical watch needs regular servicing to maintain reliability, full functionality, and accurate time-keeping. If your mechanical watch is running more than 2-3 minutes fast or slow it may be time for a full servicing.
When a watch is in for service, it is thoroughly inspected for any damaged or worn out components. The watch then goes through a full cleaning of the mechanism, after which it is regulated and re-cased. A waterproofing check is performed for every waterproof watch upon re-casing. The watch is also tested to ensure timekeeping accuracy.
The average time of repair is 7-10 days. The average service interval for a mechanical timepiece is 5-10 years between full overhauls.