New write-up on Meta-Decentralized Crypto-Currencies: http://fare.tunes.org/computing/mdcc2018.html … Fast operations by centralized notaries, secure arbitration by decentralized consensus.
As for duration: the bond should cover all transactions in the pipeline until sufficient confirmation (say the equivalent of 6 blocks in bitcoin). Each user can adjust his own trust parameters. At worst, users can just wait for consensus and not care what notaries say.
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