Pedal Harps benefit from a yearly string change and regulation, depending on how often they are being played.
The wires, in particular, lose their brightness over time.
During the regulation the discs are adjusted to improve the pitch accuracy, the pedal felts are changed and the pedal rods are adjusted.
Lever Harps will also need a string change and a lever regulation after several years of frequent playing.
The Lyon & Healy / Salvi Technicians Guild has a directory of technicians that are qualified to work on your harp.