Shops know it’s a chore that needs to be done, but the truth is compass swings are often forgotten during the final stages of avionics projects. Compass calibrations can be time consuming, but done properly the task can pay back big time if the instrument was your only means of backstopping the aircraft’s true magnetic heading.
Luckily, with a bit of knowledge and patience you can periodically check the accuracy of the instrument by swinging it yourself. Here’s a technician’s guide for tweaking the old standard.