There's something so satisfying about a fully self-contained inertial guidance system that magically knows where it is to a reasonable degree of accuracy over a

There's something so satisfying about a fully self-contained inertial guidance system that magically knows where it is to a reasonable degree of accuracy over a long period of time without any external input. Is it true AIRS was the peak of this technology (in terms of drift)? How much TLC did they need in terms of maintenance, and how reliable in practice was that complex system of 19,000 parts?