What are the replacement criteria for the gyrospheres of gyrocompasses?
Both Yokogawa and Tokyo Keiki recommend replacement every 3 years.
In practice, Yokogawa gyrospheres do indeed fail after 3 to 5 years of operation.
Tokyo Keiki sensitive elements typically last longer, up to 10 years or, sometimes, even more.
This is the experience so far, but makers can obviously change their planned obsolescence policy at any moment…
In order to maximize lifetime, it is critical to perform by-the-book maintenance once per year, using only authorized, experienced and reputable service stations.
Finally, for vessels equipped with a dual gyro system, one can more easily apply an upon-failure replacement policy, since the chances of both gyros failing simultaneously are literally negligible.