I have a concept for real-life national law, which I think would work well in nomic too. The idea is that, based on the principle that no society can morally bind its successors, laws should not automatically last more than a generation. Thus every law should expire twenty years after enactment, unless extended by a positive legislative act. Extending a law for another twenty years would be a much simpler process than enacting it again from scratch, of course, provided that it's uncontroversial. So there wouldn't be any fuss about continuing the law against murder, but a law banning demonstrations in certain places would have a harder time of being extended for another generation.
In Agora the effective generation length is much shorter, perhaps two years. I envision recording an expiry date for each Rule, which would be published in the Rulesets. Extension of the expiry date for a Rule would be by a vote resembling a Proposal, possibly actually a Proposal. Interested? If so, I'll draft a proto-Proposal. -zefram