This read-only value reports the Max Age timer advertised by the root of a specific MST instance, governing how long ports in that instance wait before assuming a path has failed. An admin checks it the same way as stpRootInformationMaxAge, but scoped to an individual instance's root rather than the CIST root. For example, confirming this matches the expected 20-second default for instance 1 rules out a misconfigured timer as the cause of slow reconvergence for that instance's VLANs.