Quartz watch movements in many fashion brands are often exchanged for brand new. The decision to repair or renew is made upon the most cost effective way for the watch and the customer. This is called module exchange or known as ‘Mod X’ in the industry.
Swiss high quality quartz watch movements are strip serviced and repaired. Worn or defective internal components such as circuits or coils are renewed as necessary.
Mechanical watches are strip serviced. Tired internal components are renewed or repaired. Parts such as train wheels are replaced when found to be worn or damaged. Mainsprings are almost always replaced at the time of service and overhaul. The balance wheel (or balance complete) which allows the workings to advance at a set amount of time, sometimes needs to be replaced also. This is a particularly high cost item especially with older and near obsolete models.